Memory devices, systems and methods employing command/address calibration

ABSTRACT

During a command/address calibration mode, a memory controller may transmit multiple cycles of test patterns as signals to a memory device. Each cycle of test pattern signals may be transmitted at an adjusted relative phase with respect to a clock also transmitted to the memory device. The memory device may input the test pattern signals at a timing determined by the clock, such as rising and/or falling edges of the clock. The test pattern as input by the memory device may be sent to the memory controller to determine if the test pattern was successfully transmitted to the memory device during the cycle. Multiple cycles of test pattern transmissions are evaluated to determine a relative phase of command/address signals with respect to the clock for transmission during operation of the system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of and claims priority to U.S. patentapplication Ser. No. 15/420,350 filed on Jan. 31, 2017, which is acontinuation of and claims priority to U.S. patent application Ser. No.15/193,128 filed on Jun. 27, 2016, which is a continuation of and claimspriority to U.S. patent application Ser. No. 14/729,058 filed on Jun. 3,2015, which is a continuation of and claims priority to U.S. patentapplication Ser. No. 14/504,087, filed on Oct. 1, 2014, which is adivisional of and claims priority to U.S. patent application Ser. No.14/295,320 filed on Jun. 3, 2014, which is a divisional of and claimspriority to U.S. patent application Ser. No. 13/430,438 filed on Mar.26, 2012, which claims the benefit of U.S. Provisional Application No.61/468,204, filed on Mar. 28, 2011, in the U.S. Patent and TrademarkOffice and Korean Patent Application No. 10-2011-0061319, filed on Jun.23, 2011, in the Korean Intellectual Property Office, the disclosures ofeach of which are incorporated herein in their entirety by reference.

BACKGROUND

The inventive concept relates to a memory devices, systems and methods,and more particularly, to command/address calibration.

In a memory system, for example, a dynamic random access memory (DRAM)system, a signal transmitted and received via a bus between a memorycontroller and a DRAM experiences propagation delays. The propagationdelays may be affected by various factors, such as interconnectioncapacitors or a parasitic capacitances existing on the bus, a substrate,or the like. As a data rate of the DRAM increases, a propagation delayand/or variations of propagation delays degrade signal integrity. It isdesirable to find an optimal signal window or compensate for signal skewbetween signals, such as between data signal and a clock signal, acommand signal and a clock signal and/or address signal and a clocksignal.

SUMMARY

Command/address calibration methods, and memory devices and memorysystems that employ command/address calibration are disclosed. Accordingto an aspect of the inventive concept, there is provided a method ofcommunication with a memory device, comprising sending a calibrationcommand over a command/address bus; sending a sequence of n first testsignals over the command/address bus, wherein n is an integer equal to 2or more; sending a clock signal over a first clock line with each of then first test signals, each of the n first test signals being sent at arespective first to nth phase with respect to the clock signal, each ofthe first to nth phases being different from one another; receiving asequence of n second test signals over a data bus respectively derivedfrom the sequence of n first test signals sent over the command/addressbus; comparing the n first test signals to the n second test signals;and determining a preferred phase of signals to be sent over thecommand/address bus with respect to the clock signal in response to thecomparing the n first test signals to the n second test the received nsecond test signals.

Each of the n first test signals comprise a first plurality of bits sentin parallel over the command/address bus may be followed by a secondplurality of bits sent in parallel over the command/address bus.

Each of the first plurality of bits and the second plurality of bits maycomprise a packet.

For each of the n first test signals, the first plurality of bits may besent at one of a rising edge of the clock signal and a falling edge ofthe clock signal, and the second plurality of bits may be sent at theother of the rising edge of the clock signal and the falling edge of theclock signal.

At least a part of the sequence of n second test signals may be receivedover a data strobe line, or received over lines dedicated to calibrationat least during a calibration mode.

The method may further comprise determining if each of the second testsignals is the same as a corresponding first test signal.

The preferred phase may be determined to correspond to one of the firstto nth phases.

Determining the preferred phase may be derived from determining asequence of phases of the first to nth phases, each phase of thesequence of phases corresponding to a second test signal determined tobe valid.

According to another aspect, a method of interface training may comprisesending a first calibration signal to a semiconductor device over acommand/address bus; sending a clock signal to the semiconductor devicewith the sending of the first calibration signal, the clock signalproviding a timing to the semiconductor device to latch logic levels ofthe first calibration signal; receiving a second calibration signal fromthe semiconductor device over a data bus, the second calibration signalbeing derived from latched logic levels of the first calibration signal;sending command and address signals over the command/address bus to thefirst semiconductor device with the sending of the clock signal, a phasebetween the command and address signals and the clock signal beingresponsive to the second calibration signal.

The method may further comprise sending a read request signal over afirst line separate from the command/address bus to the semiconductordevice while sending the first calibration signal.

The first line may be a clock enable line.

The first calibration signal may comprise a sequence of data packetstransmitted at a rate at least twice that of the period of the clocksignal.

Sending of a first calibration signal to the semiconductor device mayinclude sending a training pattern over each of multiple lines of thecommand/address bus.

The training pattern may be the same for each of the multiple lines ofthe command/address bus.

The phase between the command and address signals and the clock signalmay be individually adjusted for each of the multiple lines of thecommand/address bus.

A first signal may be sent over a first line of the command/address buswith a first phase with respect to the clock signal and a second signalmay be sent over a second line of the command/address bus with a secondphase with respect to the clock signal.

When the semiconductor device is a first semiconductor device, themethod may include sending a third calibration signal to a secondsemiconductor device over the command/address bus; sending the clocksignal to the second semiconductor device with the sending of the thirdcalibration signal, the clock signal providing a timing to the secondsemiconductor device to latch logic levels of the third calibrationsignal; receiving a fourth calibration signal from the secondsemiconductor device over the data bus, the fourth calibration signalbeing derived from latched logic levels of the third calibration signal;sending command and address signals over the command/address bus to thesecond semiconductor device with the sending of the clock signal, aphase between the command and address signals and the clock signal beingresponsive to the fourth calibration signal.

According to another aspect, a method of calibrating communication overa command/address bus of a memory device may comprise receiving a clocksignal over a clock signal line; receiving a calibration command overthe command/address bus; receiving a first test data packet over thecommand/address bus at one of a rising edge of the clock signal and afalling edge of the clock signal to generate first information;receiving a second test data packet over the command/address bus at theother of the rising edge of the clock signal and the falling edge of theclock signal to generate second information; and transmitting the firstand second information over a data bus.

The method may include receiving commands and addresses over thecommand/address bus at rising and falling edges of the clock signal.

The invention also contemplates systems and devices. For example, asemiconductor device may comprise a clock generator configured togenerate a clock signal; a clock output terminal, connected to the clockgenerator and configured to output the clock signal; a command generatorcircuit, configured to generate commands; an address generator circuit,configured to generate addresses; a plurality of command/addressterminals; a command/address buffer having an output connected to thecommand/address terminals, the command/address buffer being connected tothe command generator circuit and the address generator circuit totransmit command and address signals externally from the semiconductordevice via the command/address terminals; a phase controller configuredto control the command/address buffer to transmit a sequence of ntraining patterns over the command/address bus, n being an integergreater than 2, the phase controller configured to adjust a phase of atleast some of the n training patterns with respect to the clock signal;data terminals; and a data buffer connected to the data terminals,wherein the phase controller is configured to adjust a phase of commandand address signals with respect to the clock signal in response tofirst information received by the data buffer via the data terminals.Systems may include such devices and/or implement such methods. Theinvention is not limited to the features described in this Summary andthe scope and applicability will be apparent by reference to thefollowing detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the inventive concept will be more clearlyunderstood from the following detailed description taken in conjunctionwith the accompanying drawings in which:

FIGS. 1 and 2 are timing diagrams for describing the concept ofcommand/address calibration;

FIG. 3 is a block diagram for describing a memory system which performscommand/address calibration;

FIGS. 4A and 4B are diagrams for describing command/address calibrationsuch as that performed by the memory system shown in FIG. 3;

FIG. 5 is a block diagram of a first example of a memory system whichmay be used to implement one or more command/address calibrationembodiments described herein;

FIG. 6 is a table for describing a command/address calibration methodaccording to a first embodiment;

FIG. 7 is a diagram for describing a mode register command settingmethod according to a first embodiment;

FIG. 8 is a diagram showing an example for describing mapping betweencommand/address signals and DQ pads according to an embodiment;

FIG. 9 is a diagram showing another example for describing mappingbetween command/address signals and DQ pads according to an embodiment;

FIG. 10 is a diagram for describing a command/address calibration methodaccording to another embodiment;

FIG. 11 is a diagram showing an example for describing mapping betweencommand/address signals and DQ pads according to another embodiment;

FIG. 12 is a diagram showing another example for describing mappingbetween command/address signals and DQ pads according to anotherembodiment;

FIG. 13 is a diagram for describing a command/address calibration methodaccording to another embodiment;

FIG. 14 is a diagram for describing a mode register command settingmethod according to another embodiment;

FIG. 15 is a diagram showing an example for describing mapping betweencommand/address signals and DQ pads according to another embodiment;

FIG. 16 is a diagram showing another example for describing mappingbetween command/address signals and DQ pads according to anotherembodiment;

FIG. 17 is a diagram showing another example for describing mappingbetween command/address signals and DQ pads according to anotherembodiment;

FIG. 18 is a diagram for command/address calibration method according toanother embodiment;

FIG. 19 is a diagram showing an example for describing mapping betweencommand/address signals and DQ pads according to another embodiment;

FIG. 20 is a diagram showing another example for describing mappingbetween command/address signals and DQ pads according to anotherembodiment;

FIG. 21 is a block diagram showing another example of a memory systemwhich may be used to implement one or more command/address calibrationembodiments described herein; and

FIG. 22 is a block diagram showing another example of a memory systemthat may be used to implement one or more command/address calibrationembodiments described herein.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, exemplary embodiments of the inventive concept will bedescribed in detail with reference to the accompanying drawings, inwhich preferred embodiments of the invention are shown. The exemplaryembodiments of the inventive concept are provided to more fully describethe inventive concept to those of ordinary skill in the art. Thisinvention may, however, be embodied in different forms and should not beconstrued as limited to the exemplary embodiments set forth herein. Thatis, the exemplary embodiments are just that—examples—manyimplementations and variations are possible that do not require thevarious details disclosed herein. Various changes may be made to theinventive concept, and the inventive concept may have various forms.However, such embodiments are not intended to limit the inventiveconcept to the disclosed specific embodiments and it should beunderstood that the embodiments include all changes, equivalents, andsubstitutes within the spirit and scope of the inventive concept.Throughout the drawings, like reference numerals refer to likecomponents. In the accompanying drawings, structures may have beenexaggerated for clarity.

The terminology used herein is for the purpose of describing embodimentsonly and is not intended to be limiting of exemplary embodiments. Asused herein, the singular forms are intended to include the plural formsas well, unless the context clearly indicates otherwise. It will befurther understood that the terms “comprises,” “including” and/or “has”(and related terms) specify the presence of stated feature, number,step, operation, component, element, or a combination thereof but do notpreclude the presence or addition of one or more other features,numbers, steps, operations, components, elements, or combinationsthereof, unless otherwise noted.

It will be understood that when an element is referred to as being“connected” or “coupled” to another element, it can be directlyconnected or coupled to the other element or intervening elements may bepresent. In contrast, when an element is referred to as being “directlyconnected” or “directly coupled” to another element, there are nointervening elements present. As used herein, the term “and/or” includesany and all combinations of one or more of the associated listed itemsand may be abbreviated as “/”.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first signal could be termed asecond signal, and, similarly, a second signal could be termed a firstsignal without departing from the teachings of the disclosure.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which exemplary embodiments belong. Itwill be further understood that terms, such as those defined in commonlyused dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

From a semiconductor memory device, a high-speed operation, as well aslow power consumption, is desired. For example, a dynamic random accessmemory (DRAM) satisfying low power double data rate (LPDDR)specifications may be desired. An LPDDR DRAM system bi-directionallytransmits and receives data between a DRAM and an external device, suchas a memory controller, at both rising and falling edges of a clocksignal.

As a way to speed-up memory operations, commands and addresses may betransmitted to a memory device (e.g., a memory chip, such as a DRAM norNAND flash chip) at both rising and falling edges of a clock signal. Thememory device is configured to latch in command and/or addressinformation at both the rising edge(s) and the falling edge(s) of theclock signal. A common signal used to transmit both a command signal andan address signal is referred to as a command/address signal CMD/ADDR orCA. Pins, terminals, bus lines, internal conductors or other signalpaths that transmit the command/address signal may also be referencedherein using the acronym CA.

FIGS. 1 and 2 are timing diagrams for describing an example ofcommand/address calibration.

Referring to FIG. 1, the relative timing of a pair of clock signals(clock signal pair CK and CKB) and multiple command/address signalsCMD/ADDR may be adjusted (together or individually) through calibrationsuch that the middle of each command/address CMD/ADDR window ispositioned to optimally time an input operation, such as a latchingoperation, of the memory device. FIG. 1 represents the command/addresssignals CMD/ADDR having been adjusted so that the center portion of eachcommand/address CMD/ADDR window is at a timing when a rising edge ofclock signal CK intersects the falling edge of clock signal CKB (or viceversa—when a rising edge of clock signal CKB intersects the falling edgeof clock signal CK). The intersections may correspond to a time theclock signals CK and CKB equal each other (e.g., have the same voltagelevel). While FIG. 1 shows only command/address CMD/ADDR windows of onecommand/address CMD/ADDR signal (e.g., a signal on conductor wire of aplural conductor CMD/ADDR bus), multiple command/address CMD/ADDRsignals (e.g., multiple command/address CMD/ADDR signals received onrespective different command/address CMD/ADDR signal paths) may each bealigned as shown in FIG. 1 and the following discussion is relevant foreach such command/address CMD/ADDR signal. Command/address signal timingis adjusted or matched to rising/falling edges of the clock signals CKand CKB. As the middle of the command/address CMD/ADDR window is at aposition corresponding to an intersection between the rising and fallingedges of the clock signals CK and CKB, a timing margin of thecommand/address CMD/ADDR may be maximized or otherwise relativelyimproved. FIG. 1 may represent a relative timing of the clock signals CKand CKB and the command/address signals CMD/ADDR as seen from a memorydevice receiving these signals. The clock signals CK and CKB and thecommand/address signals CMD/ADDR may be generated by an external source(e.g., a memory controller, a CPU, a host computer, etc.), and therelative timing between clock signals CK and CKB and the command/addresssignals CMD/ADDR as generated by the external source may alter duringtransmission and thus, the relative timing as generated may be differentfrom that seen by the memory device (e.g., the relative timing generatedby the external source may be different from that shown in FIG. 1).

Due to variations between signal paths, such as variations in layout,signal driving capability, etc., a propagation time difference may begenerated between the clock signals CK and CKB and the command/addresssignal CMD/ADDR during transmission of these signals from an externalsource to a memory device. As shown in FIG. 2, the middle of thecommand/address CMD/ADDR window may precede or follow the rising andfalling edges of the clock signals CK and CKB, thereby reducing thetiming margin of the command/address CMD/ADDR.

Among four command/address signals CMD/ADDR (CA1, CA2, CA3 and CA4)shown in FIG. 2, for the first and second command/address signalsCMD/ADDR CA1 and CA2, the timing of the clock signals CK and CKB may lagmiddle of the windows of CA1 and CA2 signals. If the timing of the firstand second command/address signals CMD/ADDR CA1 and CA2 are postponedthrough calibration, the middle portion of each command/address CMD/ADDRwindow of CA1 and CA2 may be positioned to correspond to an intersectionbetween the rising edge and the falling edge of the clock signals CK andCKB. The middle portion of each command/address CMD/ADDR window of CA1and CA2 may occur with the rising/falling edges of CK and CKB whenreceived by the memory device after such postponement. For the fourthcommand/address signal CMD/ADDR CA4, the timing of the clock signals CKand CKB may be postponed or the timing of the fourth command/addresssignal CMD/ADDR CA4 may be advanced through calibration, such that themiddle of each command/address CMD/ADDR window is at a positioncorresponding to an intersection between the rising edge and the fallingedge of the clock signals CK and CKB.

FIG. 3 is a block diagram of an exemplary a memory system 10 thatperforms command/address calibration.

Referring to FIG. 3, the memory system 10 includes a memory controller20 and a memory device 30, between which are connected a clock signalline 11, a command/address bus 12, and a DQ bus 13. A clock signal CKgenerated by the memory controller 20 is provided to the memory device30 through the clock signal line 11. The clock signal CK may be providedas a continuous alternating inverted signal, together with an invertedclock signal CKB. The inverted clock signal CKB may be provided with theclock signal CK, that is, generated by the memory controller 20 andprovided to the memory device 30 (not shown in FIG. 3). Rising andfalling edges of a pair of the clock signals CK and CKB may be detectedbased on intersections between the clock signals CK and CKB, therebyimproving timing accuracy.

The single clock signal CK (without transmitting clock signal CKB) mayalso be provided as a continuous alternating inverted signal to theclock signal line 11. This implementation reduces signal lines (andterminals) between the memory device 30 and memory controller 20. Inthis case, to identify rising and falling edges of the clock signal CK,the clock signal CK and a reference voltage Vref may be compared witheach other. If noise fluctuation occurs in the reference voltage Vref, ashift occurs in detection of the clock signal CK, thereby degradingtiming accuracy when compared to the use of the pair of clock signals CKand CKB. Therefore, it may be desirable to transmit continuousalternating inverted signals that complement each other by using thepair of clock signals CK and CKB. In this case, the clock signal line 11may include two signal lines that transmit the clock signal CK and theclock signal CKB. The clock signal CK described in the embodiments ofthe inventive concept may be described as the pair of clock signals CKand CKB. For convenience's sake, the pair of clock signals CK and CKB isdescribed as the clock signal CK.

The command/address signal CA generated by the memory controller 20 isprovided to the memory device 30 through the command/address bus 12. Thecommand/address bus 12 may carry a command signal or an address signalto the memory device 30 (exclusively at any one time) and/or thecommand/address bus 12 may carry a command signal and an address signalat the same time to the memory device 30. The memory controller 20 maytransmit a mode register set (MRS) command indicating a command/addresscalibration mode through the command/address bus 12. The MRS command mayinclude a calibration mode entry command and a calibration mode exitcommand. A calibration start signal indicating the calibration modeentry command or a calibration end signal indicating the calibrationmode exit command may be transmitted through the command/address bus 12.

When the command/address bus 12 is composed of command/address signalsCA of n signal lines (e.g., conductors), where n is a natural number,and the command/address signals CA is input at rising and falling edgesof the clock signal CK (e.g., the command/address signals CA aretransmitted at a double data rate (DDR), 2n bits of command/address CAinformation may be provided through command/address buss 12 every clockcycle to the memory device 30 from the memory controller 20. Acommand/address signal CA input at the rising edge of the clock signalCK and a command/address signal CA input at the falling edge of theclock signal CK may each constitute different sets of n bits ofcommand/address CA information.

In normal operation, DQ bus 13 transmits data signals DQ between thememory controller 20 and the memory device 30 (e.g., in a writeoperation, data signals DQ are transmitted to the memory device 30 fromcontroller, and in a read operation, data signals DQ are transmittedfrom the memory device 30 to the memory controller 20). Informationregarding the command/address calibration (described in further detailbelow) may be output on the DQ bus 13 to be provided to the memorycontroller 20. The DQ bus 13 is connected to DQ pads (and/or otherdevice terminals, such as solder bumps) of both the memory controller 20and the memory device 30. Mapping of the calibration command/addressinformation signals and the DQ pads may be set in various ways.

For example, when the bit organization of the data signal DQ of thememory device 30 is x32 (DQ[31:0]), the number of DQ bus lines is 32.When the command/address bus consists of 10 conductors and thecommand/address signal CA transmits 10 bits at both the rising andfalling edges of the clock signal CK, there may be 20 bits ofcommand/address signals CA received by the memory device 30 per clockcycle of clock CK. Since the number of DQ bus lines, 32, is greater thanthe number of command/address signals, 20, each DQ bus line maycorrespond to a single one of the command/address signal bits CA,providing information of that corresponding single command/addresssignal bit (e.g., two DQ bus lines may transmit command/addressinformation regarding the command/address calibration of a single lineof the command/address bus 12). Thus, mapping may be performed suchthat, for each cycle of clock signal CK, a value of the command/addresssignals input at the rising edges of the clock signal CK is output to 10DQ pads [9:0] and a value of the 10-bit command/address signals input atthe falling edges of the clock signal CK is output to the other 10 DQpads [19:10]. Thus, while command/address CA signals may be transmittedto the memory device 30 at a double data rate (DDR) (two sets of bitsfor every cycle of clock CK), the information regarding thecommand/address calibration may be transmitted back to the memorycontroller 20 from the memory device 30 at a single data rate (SDR) (oneset of bits for every cycle of clock CK). Note that the DQ bus maytransmit data relative to a clock different from clock CK. FIG. 5,discussed further below, shows an embodiment where data is transmittedrelative to a data strobe clock DQS.

When the bit organization of the data signal DQ of the memory device 30is x16 (DQ[15:0]), the number of DQ bus lines is 16. Since the number ofDQ bus lines, 16, is less than the number of command/address signal bits(received per clock cycle CK), 20, the DQ bus lines may be insufficientto transmit information regarding the command/address calibration as oneset of bits in during one cycle of the clock CK. Thus, the DQ bus 13 maytransmit information regarding the command/address calibrationsequentially. For example, the DQ bus may transmit command/addresscalibration information regarding the 10-bit command/address signalsinput into the memory device 30 at the rising edges of the clock signalCK at one time (e.g., on DQ bus lines DQ[0:9]) and, at a later time,transmit command/address calibration information regarding the 10-bitcommand/address signals input at the falling edges of the clock signalCK (e.g., again on DQ bus lines DQ[0:9]).

FIGS. 4A and 4B are diagrams for describing command/address calibrationthat may be performed by the memory system 10 shown in FIG. 3.

Referring to FIGS. 4A and 4B, in conjunction with FIG. 3, the memorycontroller 20 detects whether a relative position (or timing) of thecommand/address signal CA window and the edge of the clock signal CK asreceived by the memory device 30 (provided from the memory controller20) is such so that the memory device 30 successfully interprets thecommand/address signal. FIGS. 4A and 4B shows several successfulinterpretations of the command/address signal as a pass (or P) andunsuccessful interpretations of the command/address signal as a fail(F). FIG. 4A represents multiple cycles of the transmission of acommand/address signal along a single command/address line ofcommand/address bus 12. Each cycle of transmitting a calibration testpattern is adjusted by the controller to change the relative phase ofthe clock CK and the command/address signal as compared to the previoustransmission cycle. The example of FIGS. 4A and 4B show this relativephase being changed by 1/20^(th) of a clock CK cycle (e.g., 18 degrees)for each subsequent transmission cycle. The relative phase may bechanged more or less each transmission cycle, depending on the accuracydesired. Note that the relative phase of the clock CK and thecommand/address signal as received by the memory device 30 for aparticular transmission cycle may not be the same as the relative phaseof the clock CK and the command/address signal as transmitted by thecontroller. Due to different characteristics of the transmission of theclock signal CK and the signal line of the command address bus 12, thetime from transmission from the controller 20 to the receipt by memorydevice 30 may differ. Such different characteristics may include adifference in signal path length, difference in conductance (e.g., dueto conductor size) of the signal path, parasitic capacitances of thesignal path (e.g., from neighboring lines), temperature, etc. The memorycontroller 20 transmits the clock signal CK to the memory device 30through the clock signal line 11 and transmits the command/addresssignal CA to the memory device 30 through a signal line of thecommand/address bus 12. The memory device 30, after receiving thephase-adjusted command/address signal CA, transmits the command/addresssignal CA as interpreted by the memory device 30 to the memorycontroller 20 through the DQ bus 13. The memory controller 20 detectswhich transmission cycles of the command/address signal successfullytransmitted their information to the memory device 30 (pass or P) andwhich of the transmission cycles were unsuccessful (fail or F).

FIG. 4A shows a clock signal (CK@Memory) and multiple a command/addresssignals received by memory device 30 over a line of the command/addressbus, received over several transmission cycles. For ease of descriptionand to better highlight the shifting of the relative phase of thecommand/address signal and the clock CK, the command/address signals areshown vertically stacked in FIG. 4A, rather than in a continuous timingdiagram, however it should be noted that each of the CA@Memory signalsshown in FIG. 4A are received sequentially in time (e.g., over the samesignal line of the command/address bus CA) in this example. In FIG. 4B,when the edge of the clock signal CK exists at a position S1 or S2 ofthe command/address signal CA, the memory device 30 may fail tosuccessfully interpret the command/address signal CA (e.g., fail tolatch the proper high or low logic of the command/address signal CA atthe window) and the memory controller 20 may decide the transmissioncycle associated with S1 and S2 as fail F. When the edge of the clocksignal CK exists at a position S3, S4, S5, S6, S7, S8, S9, S10, or S11,the memory device may successfully interpret the command/address signalCA (e.g., successfully latch the proper high or low logic of thecommand/address signal CA), and the memory controller 20 may decide thetransmission cycles associated with S3, S4, S5, S6, S7, S8, S9, S10, orS11 as pass P. When the edge of the clock signal CK exists at a positionS12, or S13 of the command/address signal CA, the memory controller 20may decide the transmission cycles associated with S12 and S13 as failF.

The description of FIGS. 4A and 4B represent that a timing of the clockCK received by the memory device 30 (CK@Memory) should have a timing sothat an edge of the clock signal CK must occur at the same time as thelogic of the command/address signal CA to be latched (e.g., occur at thecorrect logic window of the command/address signal CA). However, thisrepresentation is for ease of description and is not necessary. Thetiming of the edge of the clock signal CK may not need to be at the sametime as the logic to be latched, but may be shifted in time, forexample. For example, a clock other than CK may be responsible fortriggering the latching of the command/address signal CA by memorydevice 30. For example, an internal clock ICK may be generated by thememory device 30 in response to clock signal CK, and this internal clockICK may be used by a buffer (e.g., CA receiver 304 in FIG. 5) of thememory device 30 to latch the logic of the command/address signal CA onthe CA bus 12 at a time of a rising edge or a falling edge of ICK. Evenif the externally received clock CK and the internally generated clockICK have the same frequency and duty cycle (which may not be the case),CK and ICK may be shifted in time. Thus, edges of the external clock CKmay not occur at the same time as the logic of the command/addresssignal CA to be latched (e.g., the edges may be outside (before orafter) the window of the logic high “1” of the command/address signal CAwhich is latched by the memory device 30). As another example, even whenthe edges of clock CK are directly input to a buffer of memory device 30to trigger latching of the signal input to the memory device, there maybe some delay before the latching action is sufficient to latch thelogic of the input signal.

The memory device 30 may transmit information regarding thecommand/address calibration to the controller 20 on the data bus DQ asnoted above. For example, the memory device 30 may transmit the signalon the command/address signal line of the CA command/address bus 12 asinterpreted (e.g., as latched) by the memory device 30. Thus, during acalibration transmission cycle, if the memory controller transmits a “1”(e.g., logic high) to the memory device on a signal line of thecommand/address bus 12, but the relative phase of clock CK and thistransmission is such that the memory device 30 is triggered to latch thesignal on this signal line outside the appropriate signal window, thememory device may inaccurately interpret the transmitted signal as a“0”. Then, the memory device may transmit the value “0” over a signalline of the DQ data bus 13. The memory controller 20 may determine thetransmission associated with the transmission cycle was unsuccessful anddecide the transmission was a failure F. In a subsequent transmissioncycle during the command/address calibration, the relative phase of theclock CK and the transmission of the command/address calibration signal(e.g., the “1”) may be shifted so that memory device 30 is triggered tolatch the signal line in the signal window representing the “1”, andthis value “1” may be transmitted to the memory controller 20 (as thecommand/address calibration information). The memory controller 20 maythus compare the command/address calibration signal transmitted to thememory device 30 and the command/address calibration information (thevalue “1”) received from the memory device 30 are the same and determinethe subsequent transmission cycle to be successful (pass P).

The memory controller 20 may analyze the group of transmission cycles ofthe command/address calibration to determine a relative phase betweenthe clock CK and command/address signals to be sent on thecommand/address signal line of the command/address CA signal duringnormal operations of the memory system 10. This optimum relative phasemay be implemented by the memory controller 20 in transmitting commandand address information to the memory device 30 during normal operation.For example, the optimum relative phase may be determined by groupingall transmission cycles determined as a pass P and selecting a therelative phase of the transmission cycle in the center of this group.For example, as the transmission cycles associated with S3, S4, S5, S6,S7, S8, S9, S10, and S11 were successful (pass P) in FIGS. 4A and 4B,the memory controller 20 may select the relative phase (between clock CKand the command/address calibration signal) of the transmission cycleassociated with S7 as the optimum phase. Alternatively, the memorycontroller 20 may select the optimum phase as an average of the relativephase associated with the first and last successful transmission cycles(when the relative phases of each transmission cycle are in order (e.g.,0 degrees, 15 degrees, 30 degrees, etc.)—in the example of FIGS. 4A and4B, this would be average of the relative phase of the transmissioncycles associated with S3 and S11. Alternatively, the memory controller20 may select the optimum phase as an average of the relative phaseassociated with the last and first unsuccessful transmission cycles(when the relative phases of each transmission cycle are in order) whichsandwich the successful transmission cycles—in the example of FIGS. 4Aand 4B, this would be the average of the relative phase of thetransmission cycles associated with S2 and S12. In this way,command/address calibration may be performed.

While calibration on a single command/address signal CA (on a singleline of the command/address CA bus 12) has been described in the currentembodiment, this command/address calibration may be performed formultiple command/address signals CA transmitted through thecommand/address bus 12. This calibration may done at the same time forall of the signal lines of the command/address bus 12. The memorycontroller 20 may determine an optimum relative phase (e.g., asdescribed above) for each of the signal lines of the command/address bus20 and individually adjust the relative phase for each of the signallines of the command/address bus 20.

Alternatively, the memory controller 20 may determine an optimumrelative phase for the entire group of signal lines and select the sameoptimum phase for all the group of signal lines of the command/addressbus 12. In selecting the same optimum relative phase for the entiregroup of signal lines, the memory controller 20 may determine asuccessful transmission cycle (pass P) as one where all bits of thecommand/address calibration signal are successfully interpreted by thememory device 30 and determine an unsuccessful transmission cycle (failF) as one where at least one of the bits of the command/addresscalibration signal are unsuccessfully interpreted by the memory device30. The optimum relative phase for the entire group of signal lines maybe determined in a manner similar to that described above with respectto a single signal line of the command/address bus 12 by analyzing thepass P and fail F designations of the transmission cycles.

In another alternative, the memory controller 20 may determine anoptimum relative phase for multiple groups of signal lines comprisingthe command/address bus 12. The optimum relative phase for each of themultiple groups of signal lines may be determined as described hereinfor determining an optimum relative phase for the entire group of signallines comprising the command/address bus 12. The groups of signal linesof the command/address bus 12 may comprise a group of neighboring signallines (e.g., with no other signal lines of the command/address bus 12interposed).

In another alternative, the optimum relative phase may be determined asdescribed above for only a subset of the signal lines of thecommand/address bus 12. That is, command/address calibration signals maybe transmitted by the controller on only a subset of the signal lines ofthe command/address bus 12 and/or the memory device 30 may transmitcommand/address calibration information regarding only a subset of thesignal lines of the command/address bus. The optimum relative phase maybe determined for this subset of signal lines of the command/address bus12. The remainder of the signal lines of the command address/bus 12 mayhave an optimum phase determined based upon the optimum relative phasedetermined for the subset of signal lines. This may be done, e.g., byinterpolating (and/or extrapolating) the optimum relative phase ofimmediately neighboring signal lines (of the subset of signal lines) asan optimum relative phase. For example, if the command/address buscomprises 10 signal lines (able to send 10 parallel bits of informationat a time), the odd lines (where the signal lines are positioned in theorder of 1 to 10) may have an optimum relative phase determined asdescribed with respect to FIGS. 4A and 4B (by multiple transmissioncycles of command/address calibration signals by the controller 20 tothe memory device 30 and sending command/address calibration informationfrom the memory device 30 to the memory controller 20). Even lines ofthe command/address bus 12 may have their optimum relative phasedetermined by interpolating the previously determined optimum relativephase of the neighboring odd lines of the command/address bus 12. Thus,signal line 2 of the command/address bus 12 may have its optimumrelative phase determined as the average of the optimum relative phaseof signal lines 1 and 3. Other interpolation besides averaging ofimmediate neighbors can be performed (e.g., if signal lines 1, 2 and 3are not evenly spaced or have some known difference in length, and/orthe interpolation may include the optimum relative phase determinationsof more than two odd signal lines). Similarly, signal line 4 may haveits optimum relative phase determined by averaging or interpolating theoptimum relative phase determined for signal lines 3 and 5. As signalline 10 would not have two neighboring signal lines in this example, itsoptimum relative phase may be chosen to be the same as that of signalline 9, or may be extrapolated from multiple odd signal lines (e.g.,from signal lines 7 and 9).

FIG. 5 is a block diagram of an example of the memory system 10 whichmay be used to implement any command/address calibration embodimentdescribed herein.

Referring to FIG. 5, the memory system 10 includes memory controller 20and memory device 30. The memory controller 20 may include a clockgenerator 201, a command/address generator 202, a command/addresstransmitter 203, which hereinafter may be referred to as a CAtransmitter, a register 204, a comparator 206, a phase/timing controller208, and an input/output unit 210.

The memory controller 20 provides the clock signal CK generated from theclock generator 201 to the memory device 30 through the clock signalline 11. The command/address generator 202 generates an initialcommand/address signal CA0 and provides the same to the CA transmitter203.

The CA transmitter 203 receives an initial command/address signalCA_(sp1) having a first phase p1, and adjusts a phase or timing of theinitial command/address signal CA_(sp1) in response to a control signalCTRL of the phase/timing controller 208 to generate a phase adjustedcommand/address signal CA_(sp2) with a second phase p2. CA transmitter203 may also be controlled by control signal CTRL to substantiallymaintain the phase of the initial command/address signal CA so that thefirst phase p1 is substantially the same as the second phase p2 (forease of explanation, signal CA_(sp2) is referred to as a phase adjustedcommand/address signal CA even though in certain circumstances, theinitial command/address CA_(sp1) signal may not have a phaseadjustment). The phase adjusted command/address signal CA_(sp2) is sentto the register 204 and the information represented by phase adjustedcommand/address signal CA_(sp2) is stored in the register 204 as CA_(s).The phase adjusted command/address signal CA_(sp2) is provided to thememory device 30 through the command/address bus 12. The phase adjustedcommand/address signal CA_(sp2) is provided to the memory device 30,together with the clock signal CK.

The register 204 stores the information of the phase adjustedcommand/address signal CA_(sp2) as sent command/address informationCA_(s). The comparator 206 compares sent command/address informationCA_(s) stored in the register 204 with received command/addresscalibration information CA_(r) (received by memory device 30 andtransmitted back to memory controller 20 as described herein) outputfrom the input/output unit 210. The comparator 204 compares informationCA_(s) with information CA_(r) to generate a pass or fail signal P or F.

The phase/timing controller 208 generates the control signal CTRLinstructing a phase shift of the initial command/address signal CA_(sp1)according to the pass or fail information P or F generated by thecomparator 206. The control signal CTRL is provided to the CAtransmitter 203, and the phase or timing of the initial command/addresssignal CA_(sp1) is adjusted to generate the phase-adjustedcommand/address signal CA_(sp2).

In a normal operation mode, the data input/output unit 210 receives readdata R_Data1 transmitted from the memory device 30 through the DQ bus 13or transmits write data W_Data1 to be written to the memory device 30through the DQ bus 13. In addition, in the command/address (CA)calibration mode, the data input/output unit 210 may receivecommand/address calibration information CA_(r) corresponding to thephase-adjusted command/address signal CA_(sp2) received by the memorydevice 30 from the memory controller 20 through the DQ bus 13. Thecommand/address calibration information CA_(r) may be the informationlatched in by memory device 30 in response to clock CK (e.g., with therising and/or falling edge of clock CK) when the phase-adjustedcommand/address signal CA_(sp2) is being sent to the memory device 30.CA_(r) may be the same information as CA_(s) when the timing of CK issuch to properly interpret (or latch) the phase-adjusted command/addresssignal CA_(sp2) or CA_(r) may be different than CA_(s) when the memorydevice 30 incorrectly interprets the phase-adjusted command/addresssignal CA_(sp2). The data input/output unit 210 outputs thecommand/address signal information CA_(r) to the comparator 206.

The input/output unit 210 may include an input buffer 212, a selectionunit 214, and an output buffer 216. The input buffer 212 and outputbuffer 216 may comprise latches and/or amplifiers to respectively latchand/or amplify received signals. The input buffer 212 is connected toreceive data and command/address calibration information CA_(r)transmitted through the DQ bus 13 from memory device 30. The selectionunit 214 transmits the data received by the input buffer 212 as readdata R_Data1 to an internal circuit block (not shown) of the memorycontroller 20 in response to a first selection signal SEL1 in the normaloperation mode, or transmits the command/address calibration informationCA_(r) received by the input buffer 212 to the comparator 206 inresponse to the first selection signal SEL1 in the CA calibration mode.The selection unit 214 may be multiplexer. The input buffer 212 mayinterpret the command/address calibration information CA_(r) correctlythe DQ bus 13 has been calibrated in a DQ calibration mode prior to theCA calibration mode and/or the transmission of command/addresscalibration information CA_(r) on the DQ bus 13 to the input buffer 212is at a slower rate to assure latching of the information on the DQ busat 13 the correct window (e.g., the slower rate of transmission is at ansingle data rate (SDR) when the command/address calibration is at adouble data rate (DDR)). In this instance, the command/addresscalibration information CA_(r) received on the DQ bus 13 is the same asthe command/address calibration information CA_(r) transmitted by thedata input/output unit 210 to the CA comparator 206. The output buffer216 transmits the write data W_Data1 to be written to the memory device30 through the DQ bus 13.

The memory device 30 includes a clock buffer 302, a command/addressreceiver 304, which will hereinafter be referred to as a CA receiver304, and a data input/output unit 310. The clock buffer 302 receives theclock signal CK transmitted through the clock signal line 11 to generatean internal clock signal ICK. The phase adjusted command/address signalCA_(sp2) is transmitted to the memory device 30 through thecommand/address bus 12. The CA receiver 304 generates thecommand/address calibration information CA_(r) in response to theinternal clock signal ICK, which may occur when enabled by a chipselection signal /CS and a clock enable signal CKE. The chip selectionsignal /CS and the clock enable signal CKE may be provided separatelyfrom the command/address signal line 12, as in FIG. 5, or may be carriedon the command/address signal line 12 for transmission to the memory 30,unlike as shown in FIG. 5.

The clock enable signal CKE may be used as a pseudo command which actsas a read command of the phase adjusted command/address signal CA_(sp2)transmitted through the command/address bus 12 in the CA calibrationmode. The CA receiver 304 generates the command/address calibrationinformation CA_(r) according to the phase adjusted command/addresssignal CA_(sp2) latched based on a timing of ICK (e.g., a rising edgeand/or falling edge) received when the clock enable signal CKE is in anactive state and when memory device 30 is enabled by the chip selectionsignal /CS. The command/address calibration information CA_(r) isprovided to the data input/output unit 310.

The data input/output unit 310 is connected to receive thecommand/address calibration information CA_(r) and read data R_Data2transmitted from an internal circuit block (e.g., data read pathcircuitry connected to a memory array that stores the read data R_Data2)(not shown) of the memory device 30 and transmits the received read dataR_Data2 to the DQ bus 13 in response to a second selection signal SEL2in a normal read operation mode, or transmits the second command/addresssignal CA2 to the DQ bus 13 in response to the second selection signalSEL2 in a calibration mode. The data input/output unit 310 receiveswrite data W_Data1 to be written to the memory device 30 through the DQbus 13 and transmits the received write data W_Data1 to the internalcircuit block of the memory device 30 in a normal write mode. The datainput/output unit 310 includes a selection unit 312, an output buffer314, and an input buffer 316. The selection unit 312 selects one of thesecond command/address signal CA2 output from the command/addressreceiver 304 and the read data R_Data2 provided from the internalcircuit block of the memory device 30, in response to the secondselection signal SEL2, and transmits the selected signal or data to theoutput buffer 314, according to the normal operation mode or thecalibration mode. The selection unit 312 may be a multiplexer.

The output buffer 314 transmits the command/address calibrationinformation CA_(r) or the read data R_Data2 output from the selectionunit 312 to the DQ bus 13. The input buffer 316 receives datatransmitted through the DQ bus 13 and transmits the receive data aswrite data W_Data2 to the internal circuit block of the memory device30. For example, the write data W_Data2 may be transmitted via datawrite path circuitry to a memory array to be written into the memoryarray. The data write path circuitry and the data read path circuitrymay share circuitry.

In the current embodiment, the command/address calibration informationCA_(r) output from the output buffer 314 of the memory device 30 isprovided to the memory controller 20 through the DQ bus 13. Also,command/address calibration information CA_(r) output from the outputbuffer 314 of the memory device 30 may be provided to the memorycontroller 20 through a data strobe (DQS) line(s) and the DQ bus 13. Thedata input/output unit 210 of the memory controller 20 and the datainput/output unit 310 of the memory device 30 may be connected to eachother through the DQS line(s) and the DQ bus 13.

CA calibration in the memory system 10 may be performed as below. The CAtransmitter 203 of the memory controller 20 generates thecommand/address signal CA_(sp2) by adjusting the phase or timing of theinitial command/address signal CA_(sp1) in response to the controlsignal CTRL of the phase/timing controller 208. The control signal CTRLmay also have a value that maintains the phase of command/addresssignal, as noted previously. The CA receiver 304 of the memory device 30receives the phase adjusted command/address signal CA_(sp2) at a timingin accordance with the internal clock signal ICK and when enabled by theclock enable signal CKE to generate the command/address calibrationinformation CA_(r). The command/address calibration information CA_(r)of the memory device 30 is transmitted to the DQ bus 13 in response tothe second selection signal SEL2. Before calibration of command/addresssignals, a value of the phase adjusted command/address signal CA_(sp2)transmitted from the memory controller 20 and a value of thecommand/address calibration information CA_(r) interpreted (e.g.,latched) by the memory device 30 may be different from each other, e.g.,due to noise generated during signal transmission and/or variations insignal transmission timing between clock CK and signals transmitted bythe CA bus 12. Calibration of the command/address signals addresses thisproblem.

The memory controller 20 transmits the command/address calibrationinformation CA_(r) to the comparator 206 received via the DQ bus 13 inresponse to the first selection signal SEL1 in the command/addresscalibration mode. If the DQ bus 13 calibrated in a DQ calibration modeprior to the CA calibration mode, then the chance of incorrectlyinterpreting the command/address calibration information CA_(r) by thememory controller 20 (e.g., as interpreted by input buffer 212) isreduced. The comparator 206 compares a value of the command/addresssignal CA_(sp2), transmitted by the memory controller 20 to the memorydevice 30 and stored in the register 204, with a value of thecommand/address calibration information CA_(r) received by the memorycontroller and, generates a pass signal P if they are the same as eachother and a fail signal F if they are different. The phase/timingcontroller 208 generates the control signal CTRL instructing a new phaseshift of the initial command/address signal CA_(sp1) (to obtain a newphase adjusted command/address signal CA_(sp2) having a new relativephase difference with clock CK) and repeats the process for the newinitial command/address signal CA_(sp1) having a different relativephase with respect to clock CK. After multiple cycles of this process(each with a different phase shift of the initial command/address signalCA_(sp1) by the CA transmitter 203) the controller analyzes the group ofpass P and fail F signals to determine the optimal relative phase of theCA signal line (or lines or bus) for normal operation. Although notshown in FIG. 5, the control signal CTRL may be transmitted to the clockgenerator 201 to adjust the timing or phase of the clock signal CK toadjust the relative phase of the command/address signal and the clocksignal CK.

By repeating the foregoing CA calibration, the phase/timing controller208 of the memory controller 20 determines that the optimum timing(e.g., the middle of the passed P positions) to time the input (e.g.,latching) of the command/address signal to the middle portion of thecommand/address signal CA window, and generates a command/address signalCA such that the middle of the command/address signal CA windowcorresponds to such input by the memory device 30 (which may correspondto an edge of the clock signal CK), and provides the generatedcommand/address signal CA and clock CK to the memory device 30 with theoptimum relative phase between the command/address signal CA and clockCK. Thus, when the timing of the input (e.g., latching) of thecommand/address signal corresponds to the edge(s) of the clock signal CKreceived by the memory device 30, the memory device 30 receives thecommand/address signal CA for which the middle of an effective windowcorresponds to rising and falling edges of the clock signal CK, strictlyspeaking, rising and falling edges of the clock signals CK and CKB.

While calibration on the single command/address signal on a single lineof the command/address bus 12 has been described, such calibration maybe performed for plural or all of the lines of command/address bus asnoted previously.

FIG. 6 is a diagram for describing an exemplary command/addresscalibration method. FIG. 6 is a timing diagram for describing acommand/address calibration method that may be implemented in the memorysystem 10, in which the bit organization of the data DQ of the memorydevice 30 is x32 (the DQ bus is composed of 32 DQ signal lines connectedto 32 DQ terminals (e.g., pads, bumps, etc.) of the memory device 30 and32 DQ terminals of the memory controller 20.

Referring to FIG. 6, in conjunction with FIG. 5, the memory controller20 generates the clock signal CK for the memory device 30. The memorycontroller 20 sends an enter command/address calibration modeinstruction to the memory device 30. The memory controller 20 transmitsthe enter command/address calibration mode instruction through thecommand/address bus 12. The enter command/address calibration modeinstruction may be input using a mode register set (MRS) command formatto program a mode register of the memory device to indicate acommand/address calibration mode. The memory device 30 may be responsiveto the mode register set information to respond to the command/addresscalibration mode indication to enter the command/address calibrationmode. The memory controller 20 may transmit the command/address endsignal through the command/address bus 12. The command/address endsignal may be input using a MRS command indicating exit from thecalibration mode.

At time t₀, the command/address calibration start signal is receivedthrough the command/address bus 12 at the memory device, together withactivation of a logic low level of the chip selection signal /CS. Arising edge of clock signal CK received by the memory device 20 triggersthe latching of the enter command/address calibration mode instruction.For example, a first mode register command (MRW#41) is transmitted asthe enter command/address calibration mode instruction. Whencommand/address signals CA[9:0] of 10 bits are carried on thecommand/address bus 12, the MRW#41 command may comprise command/addresssignals CA[3:0] to indicate the command is a mode register settingcommand, and command/address signals CA[9:4] to indicate the moderegister setting command is a command to enter into command/addresscalibration mode.

In this example, the MRW#41 command is input at both the rising andfalling edges of the clock signal CK; in FIG. 6, the MRW#41 command isfirst latched by the memory device in response to the rising edge ofclock CK at time t₀ and is latched a second time by the memory device 30in response to the immediately subsequent falling edge of the clock CK.That is, the same MRW#41 command is input at the rising and fallingedges of the clock signal CK corresponding starting at time t₀ of theclock signal CK. This is because, when an MRS command is input at adouble data rate (DDR) through a command/address signal line, an errormay be generated such that a memory device having a high operationfrequency misses the MRS command. Also, a different command may beerroneously interpreted as the enter command/address calibration modecommand. To reduce the possibility of error, the same MRW#41 command isinput at the rising and falling edges of the clock signal CKcorresponding to the timing t₀ of the clock signal CK. That is, as thesame command/address signal is input at the rising edge and the fallingedge of the clock signal CK, a similar result as in transmission at asingle data rate (SDR) may be obtained and a failure in entering thecalibration mode (or an unintended entry into calibration mode),especially caused when the command/address signal line is not yetcalibrated, may be reduced.

After a delay of a predetermined time from the time t₀ when the MRW#41command is first input, the clock enable signal CKE is activated (activewith a low logic level during address/command calibration in FIG. 6)together with activation of the logic low level of the chip selectionsignal /CS. At time t₁ command/address signal CAxR is sent by memorycontroller 20 and received by memory device 30, followed subsequently bythe transmission and receipt of CAxF at the next half clock period (herethe immediate subsequent edge of the clock CK). The command/addresssignals CAxR and CAxF are transmitted from the memory controller 20 tothe memory device 30 through the command/address bus 12. The time tMRWmay be a mode register set write cycle time to provide sufficient timefor the memory device 30 to write indication data to the mode registerset of the memory device 30.

In this example, command/address signals CAxR constitute a plurality ofsignals transmitted on all lines of the command/address bus 12 that areinput at the rising edge of the clock signal CK, and the command/addresssignals CAxF constitute a plurality of signals transmitted on all linesof the command/address bus 12 that are input at the falling edges of theclock signal CK. The pair of CAxR and CAxF may constitute acommand/address test pattern signal that is transmitted to the memorydevice during the command/address calibration to determine if the memorydevice properly interprets the information represented by the testpattern signal. In the example of FIG. 6, the test pattern (sent foreach relative phase sequence) comprises a sequence of two bits (twologic windows of the command/address calibration signal) for eachcommand/address signal line of the command/address bus 12. However, thetest pattern may comprise a sequence of more than two bits, or maycomprise one bit (the description with respect to FIGS. 4A and 4B mayimply a one bit test pattern in the transmission of the phase adjustedcommand/address signal CA_(sp2), however, phase adjusted command/addresssignal CA_(sp2) may be a one bit, two bit, or more than two bit sequencesent over each (or some) of the lines of the command/address bus 12).The command/address signal CAxR and the command/address signal CAxFinput to the memory device 30 through the command/address bus 12 may bedifferent signals representing different sets of bits. For example, whenthe command/address bus 12 is composed of command/address signalsCA[9:0] of 10 bits, the command/address signal CAxR of 10 bits and thecommand/address signal CAxF of 10 bits may be distinguished as differentsignals. Thus, the command/address calibration signals CA[9:0] of 20bits may be input to the memory device 30 through command/addressterminals (pins, pads, solder bumps, etc.) (not shown) of the memorydevice 30 connected with the command/address bus 12 of 10 bits. Thememory device 30 may input (e.g., latch) the command/address calibrationsignals at a timing determined by the edges clock CK (e.g., at the sametime or at a predetermined or fixed time before or after the appropriatetriggering edge of clock CK). The memory device 30 may transmit theinputted command calibration signals (as interpreted by the memorydevice—which may be interpreted correctly or incorrectly) to the memorycontroller 30, as noted above, for example, with respect to FIGS. 4A, 4Band/or 5.

As there is a demand for the memory device 30 to have large capacity,the degree of integration and the number of memory cells increase. Asthe number of memory cells increases, the number of address bits foraddressing the memory cells also increases. The increase in the numberof address pins leads to the increase in chip size. Therefore, a methodfor suppressing the increase in the number of address pins required mostin a memory chip is needed. Since command/address signals are input atboth rising and falling edges of a clock signal in this example, thenumber of command/address pins of the memory device 30 may be reduced.

In this example, during calibration mode of the command/address bus, aread command cannot be transmitted from the memory controller 20 throughthe command/address signal line. Thus, the clock enable signal CKE actsas a read command of the command/address signals CAxR and CAxF in thecalibration mode of the command/address signal bus. When the clockenable signal CKE is activated at a logic low level, the command/addresssignals CAxR and CAxF are input at a timing determined by the edges ofclock CK and results thereof are output through data bus DQ 13 to thememory controller 20. Thus, the clock enable signal CKE is used as apseudo command and enables the memory device to input thecommand/address calibration test pattern (e.g., signals CAxR and CAxF).The phase adjusted command/address signal CA_(sp2) transmitted from thememory controller 20 in the embodiment described with respect to FIG. 5corresponds to the value of the command/address signals CAxR or CAxF . .. CAyR and CAyF in FIG. 6 (hereinafter, generically referred to as CAnRand CAnF). Each CAnR and CAnF pair correspond to a cycle of atransmission of a phase adjusted command/address signal CA_(sp2), eachcycle transmitting the command/address signal CAnR and CAnF signal pairwith a new relative phase difference with respect to clock CK ascompared to previous CAnR and CAnF signals. The adjusted phasedifference for each CAnR and CAnF signal pair is not shown in FIG. 6 forease of explanation (see FIGS. 4A and 4B and related description). Thus,n (n being an integer equal to two or more) test command/address testpattern signals (e.g., n CAnR and CAnF signal pairs) may be sent overthe command/address bus with a clock signal, where each of the n testpattern signals being sent a different respective first to nth phasewith respect to the clock signal.

At time t₃, after a delay of time tADR from time t₁ of the clock signalCK at which the clock enable signal CKE is activated, the value of thecommand/address calibration test pattern CAxR and CAxF input by thememory device 30 as interpreted (e.g., latched) by the memory device 30(corresponding to command/address calibration information CA_(r)) isoutput from the memory device 30 to the memory controller 20 in thecommand/address signal CAxR or CAxF through the DQ bus 13. Time tADR maybe predetermined, and based on a known timing of the operation of thememory device. (Note that in FIG. 6, the portions of the timing diagramillustrating the timings of CK, CA CS and CKE in vertical alignment withthe dashed line representing time t₃ are at a later time than time t₃ asrepresented by the break symbol in these timings.) As shown in FIG. 6,the values of the command/address signal CAxR input by the memory device30 (e.g., command/address calibration information associated with CAxR)triggered by the rising edge of clock CK are output on the “even DQ”lines of the DQ bus 13 (DQ0, DQ2, etc.) over a time period during whichplural clock edge of clock CK occur. In this instance, the time of thecommand/address calibration information output to the memory controller20 may occur over plural periods of clock CK. As shown by FIG. 6, thevalues of the command/address signal CAxF input by the memory device(e.g., command/address calibration information associated with CAxF) areoutput on DQ bus 13 at the same time and manner as the values of thecommand/address signal CAxR input by the memory device 30, except theyare output on the “odd DQ” lines of the DQ bus 13. When viewed from atop down view, the DQ bus lines may (but need not) run substantially inthe same directions between the memory device 30 and the controller 20and be numbered from 0 to m, where m+1 is the number of bus lines of theDQ bus.

If the relative phase of the clock CK and the address/commandcalibration test pattern signal CAxR and CAxF triggers input (e.g.,latching) of the address/command calibration test pattern signal CAxRand CAxF at the correct logic window, the memory device should correctlyinterpret the calibration test pattern signal. In this instance, thememory controller 20 would determine a pass P (for the relative phase ofthe clock CK and the address/command calibration test pattern signalCAxR and CAxF test pattern signal). If the relative phase of CK and CAxRand CAxF signals results in an incorrect interpretation of theinformation represented by the address/command calibration test patternsignal CAxR and CAxF, the memory controller 20 would determine a fail F.

Mapping between DQ pads and the calibrated command/address signals CAxRand CAxF for transmitting the value of the second command/address signalCA2 received by the memory device 30 to the memory controller 20 throughthe DQ line may be set in multiple ways. An example of mapping is shownin FIG. 8 where values of the command/address signal CAxR input by thememory device 30 at the rising edge of the clock signal CK (bits CA0 toCA9) may be output to memory device 30 DQ pads DQ[9:0] and values of thecommand/address signal CAxF input by the memory device 30 at the fallingedges of the clock signal CK may be output to memory device DQ padsDQ[19:10]. Another example of mapping is shown in FIG. 9 where a valueof a command/address signal CA9 among the command/address signals CAxRinput at the rising edges of the clock signal CK may be output to a DQSpad DQS0 of the memory device 30 and values of command/address signalsCA[8:0] may be output to memory device 30 DQ pads DQ[8:0]. A value ofthe command/address signal CA9 among the command/address signals CAxFinput at the falling edges of the clock signal CK may be output to a DQSpad DQS1 of the memory device and values of the command/address signalsCA[8:0] may be output to memory device DQ pads DQ[17:9].

At the memory controller 20, the relative phase between clock CK and thephase adjusted command/address signal (e.g., CAyR and CAyF) sent to thememory device 30 is altered, and a new cycle of the command/addresscalibration is implemented. As shown in FIG. 6, an example of anintermediate cycle of transmitting command/address calibration signalsCAyR (at time t₄) and CAyF (at the immediately subsequent clock edge ofCK) to the memory device 30 on the command/address bus 12, and sendingthe values interpreted by the memory device 30 to the memory controller20 by the memory device in a manner similar to that described above withrespect to CAxR and CAxF and a repetitive description here is thusunnecessary.

Just prior to time t₅, the clock enable signal CKE is deactivated,together with activation of the logic low level of the chip selectionsignal /CS. This may occur when the command/address calibration signalCAnR and CAnF (the last of n command/address calibration informationsets transmitted from the memory device 30 to the controller 20 for thecommand/address calibration session) are transmitted from the memorycontroller 20 to the memory device 30 through the command/address bus12. The command/address calibration information CAnR and CAnF may betransmitted in the same manner as transmission of the command/addresscalibration information CAxR and CAxF.

At a timing t₅, the end command/address calibration mode command istransmitted through the command/address bus 12 together with activationof the logic low level of the chip selection signal /CS. (Note that thetimings illustrated in FIG. 6 for Even DQ and Odd DQ in verticalalignment with time t₅ occur previous to time t₅—see break notations inthe Even DQ and Odd DQ timings.) For example, a second mode register(MRW#42) command is transmitted as the end command/address calibrationmode command. If the command/address signals CA[9:0] of 10 bits arecarried on the command/address bus 12, the MRW#42 command may comprisecommand/address signals CA[3:0] to identify the command as a moderegister setting command and command/address signals CA[9:4] to identifythe mode register setting command as an end command/address calibrationmode command.

The MRW#42 command is input at both the rising and falling edges of theclock signal CK corresponding to the timing t₅. That is, the same MRW#42command is input twice at both the rising edge of the clock signal CK attime t₅ and at the immediately subsequent falling edge of the clocksignal CK. When an MRS command is input using the command signal at aDDR, an error may be generated such that a memory device having a highoperation frequency misses the MRS command. To reduce the chances ofthis error, the same MRW#42 command is input twice at the rising andfalling edges of the clock signal CK.

There are many ways for the memory device to determine when to latch theexit command/address calibration mode command (here, MRW#42). In oneimplementation, the memory device may be configured to latch theinformation provided on the CA bus 12 at edges of the clock signal CKhaving a predetermined relationship (e.g., timing) with respect to thetransition of the clock enable signal CKE from the active low state tothe high state. For example, as shown in FIG. 6, the memory device maybe configured to latch the information provided on the CA bus 12 at thetwo edges of clock CK immediately following the transition of the clockenable signal CKE from the active low state to the high state. As CKE ishigh, the memory device 30 treats the information on the command addressbus CA 12 as a command (to be processed, e.g., by a command decoder ofthe memory device 30) rather than as a calibration test pattern. Itshould be noted as well that the clock enable signal CKE may beconsidered active low only during certain operations, such as onlyduring the CA calibration mode, and at other times, be interpreted as anactive high signal.

After a delay of a predetermined time tMRZ from time t₅ at which theMRW#42 command is input, the output of the command/address signals CAnRand CAnF to the memory device DQ pads is terminated. A period from thetiming t₀ of the clock signal CK at which the MRW#41 command, which isthe command/address calibration start signal, is input to time t₅ of theclock signal CK at which the MRW#42 command is input plus time tMRZ maybe the CA calibration period.

FIG. 7 is a truth diagram for describing an exemplary mode registercommand setting method.

Referring to FIG. 7, the MRW#41 command and the MRW#42 command may beset by the clock enable signal CKE, the chip selection signal /CS, andthe command/address signals CA[9:0]. The MRW#41 command may act to setthe MRS register (e.g., write to the MRS register) of the memory device30 when the clock enable signal CKE is at a logic high (H) level, thechip selection signal /CS is at a logic low (L) level, thecommand/address signals CA[3:0] are at a logic low (L) level, and thecommand/address signals CA[9:4] are at logic levels of H-L-H-L-L-H. Thatis, the MRW#41 command may comprise the command/address signals CA[9:0]29H. The same MRW#41 command may be sent to the memory device twice ontothe command/address bus 12 at both the rising and falling edges of theclock signal CK. The memory device 30 may be configured to set the moderegister to indicate the memory device 30 is in a command/addresscalibration command when at least one of the two MRW#41 commands sent tothe memory device 30 is properly interpreted when input by the memorydevice 30. (Note that sending two MRW#41 commands to the memory device30 may comprise maintaining the command sent on the command/address buswithout alteration over two logic windows of the command/addresssignals—which may comprise a full clock period of clock CK.)

The MRW#42 command may act to set the MRS register of the memory device30 when the clock enable signal CKE is at a logic high level, the chipselection signal /CS is at a logic low level, the command/addresssignals CA[3:0] are at a logic low level, and the command/addresssignals CA[9:4] are at logic levels of H-L-H-L-H-L. That is, the MRW#42command may comprise the command/address signals CA[9:0] 2AH. The sameMRW#42 command may sent to the memory device twice on thecommand/address bus 12 at both the rising and falling edges of the clocksignal CK. Herein, the command/address signals CA[9:4] may be used asmode register setting addresses MA[5:0].

FIG. 8 is a diagram showing an example for describing mapping betweencommand/address signals and DQ pads, according to an embodiment. Sincethe command/address signals CA[9:0] are input at both the rising andfalling edges of the clock signal CK in the current embodiment, thecommand/address signals CA[9:0] may be composed of 20 bits. In thisregard, the bit organization of the data DQ of the memory device 30 isx32 and thus the number of DQ pads is 32. The number of DQ pads isgreater than the number of command/address signals, such that the DQpads may correspond to the command/address signals one-to-one.

Referring to FIG. 8, values of the command/address signals CA[9:0] inputat the rising edges of the clock signal CK may be mapped to be output tothe DQ pads DQ[9:0]. Values of the command/address signals CA[9:0] inputat the falling edges of the clock signal CK may be mapped to be outputto the DQ pads DQ[19:10]. For example, in FIG. 6, values of thecommand/address signals CAxR input at the rising edges of the clocksignal CK corresponding to the timing t₁ are output to the DQ padsDQ[9:0], and values of the command/address signals CAxF input at thefalling edges of the clock signal CK corresponding to the timing t₁ areoutput to the DQ pads DQ[19:10]. The values of the command/addresssignals CAxR input at the rising edges of the clock signal CKcorresponding to the timing t₄ are output to the DQ pads DQ[9:0], andvalues of the command/address signals CAxF input at the falling edges ofthe clock signal CK corresponding to the timing t₄ are output to the DQpads DQ[19:10].

FIG. 9 is a diagram showing another example for describing mappingbetween command/address signals and DQ and DQS pads according to anotherembodiment.

Referring to FIG. 9, values of the command/address signals CA[9:0] inputto the memory device 30 at the rising edges of the clock signal CK (e.g.CAxR) may be mapped to be output to the DQS pads DQS0 and DQS1, and theeven DQ pads DQ[0, 2, 4, 6, 8, 10, 12 and 14]. That is, the input valueof the command/address signal CA9 is output to the DQS pad DQS1, theinput value of the command/address signal CA4 is output to DQS0, theinput values of the command/address signals CA[3:0] are respectivelyoutput to the DQ pads DQ[6, 4, 2, 0] and the input values of thecommand/address signals CA[8:5] are respectively output to the DQ padsDQ[14, 12, 10, 8].

Values of the command/address signals CA[9:0] input to the memory device30 at the falling edges of the clock signal CK (e.g., CAxF) may bemapped to be output to the DQS pads /DQS0 and /DQS1 and the DQ padsDQ[17:9]. That is, the input value of the command/address signal CA9 maybe output to the DQS pad /DQS1, the input value of CA4 may be output toDQS pad /DQS0, the input values of the command/address signals CA[3:0]are respectively output to the DQ pads DQ[7, 5, 3, 1] and the inputvalues of the command/address signals CA[8:5] are respectively output tothe DQ pads DQ[15, 13, 11 and 9].

FIG. 10 is a diagram for describing a command/address calibration methodaccording to another embodiment.

FIG. 10 is a timing diagram for describing a command/address calibrationmethod in the memory device 30, in which the bit organization of thedata DQ of the memory device 30 is x32.

Referring to FIG. 10, in conjunction with FIG. 5, the memory controller20 generates the clock signal CK for the memory device 30. The memorycontroller 20 issues an enter command/address calibration mode command(or instruction) to the memory device 30 through the command/address bus12. The enter command/address calibration mode command may be inputusing the particulars of the MRS command described herein with respectto other embodiments. The memory controller 20 transmits the exitcommand/address calibration mode command (or instruction) through thecommand/address bus 12. The exit command/address calibration modecommand may be input using the particulars of the MRS command describedherein with respect to other embodiments.

At the timing t₀ of the clock signal CK, the MRW#41 command, which isthe enter command/address calibration command, is transmitted throughthe command/address bus 12, together with activation of a logic lowlevel of the chip selection signal /CS. For example, the MRW#41 commandis input at both the rising and falling edges of the clock signal CKstarting at time t₀. That is, the same MRW#41 command may be input atthe rising and falling edges of the clock signal CK starting at time t₀.

At the timing t₁, after a delay of the time tMRW from t₀ of the clocksignal CK at which the MRW#41 command is input, the clock enable signalCKE is activated with a predetermined pulse width for one cycle of theclock signal CK, together with activation of the logic low level of thechip selection signal /CS, and the command/address signals CAxR and CAxFare transmitted in sequence through the command/address bus 12.

The command/address signals CAxR are input at the rising edge of theclock signal CK at time t₁, and the command/address signals CAxF areinput at the falling edge of the clock signal CK at the immediatelysubsequent falling edge of clock CK after time t₁. The command/addresssignal CAxR and the command/address signal CAxF input through thecommand/address bus 12 may be different signals representing differentinformation, such as different test pattern information.

In the calibration mode, the clock enable signal CKE acts as a readcommand of the command/address signals CAxR and CAxF corresponding tothe value of the second command/address signal CA2 received by thememory device 30 in FIG. 5. During command/address calibration mode (andwhen the chip select /CS is active (logic low)), the memory deviceinterprets an activation of the clock enable signal CKE at a logic lowlevel as an instruction to input signals on the command/address signalbus at the subsequent edges of clock signal CK, and thus the value ofthe command/address signal CAxR or CAxF as received by the memory device30 are input, e.g., as show in FIG. 10.

Starting at time t₃, after a delay of the time tADR from time t₁, thevalues of the command/address signals CAxR and CAxF (asinterpreted/input by the memory device) are output to the DQ pads. Atthe timing t₃, the input command/address signals CAxR are output to evenDQ pads and during the immediately subsequent clock edge of clock CK,the input command/address signals CAxF are output to odd DQ pads.

Mapping between the command/address signals CAxR and CAxF and the DQpads may be set in various ways. An example of mapping is illustrated inFIG. 11 where values of the command/address signals CAxR input at therising edges of the clock signal CK may be output to even DQ padsDQ[2n], where n is 0 to 9, and values of the command/address signalsCAxF input at the falling edges of the clock signal CK may be output toodd DQ pads DQ[2n+1], where n is 0 to 9.

As another example of mapping, results of calibration on thecommand/address signals CA[3:0] among the command/address signals CAxRinput at the rising edges of the clock signal CK may be output to evenDQ pads DQ[2n], where n is 0 to 3, a value of a command/address signalCA4 may be output to the DQS pad DQS0, values of command/address signalsCA[8:5] may be output to even DQ pads DQ[2n], where n is 4 to 7, and avalue of the command/address signal CA9 may be output to the DQS padDQS1. Values of the command/address signals CA[3:0] among thecommand/address signals CAxF input at the falling edges of the clocksignal CK may be output to odd DQ pads DQ[2n+1], where n is 0 to 3, avalue of the command/address signal CA4 may be output to the DQS pad/DQS0, values of command/address signals CA[8:5] may be output to odd DQpads DQ[2n+1], where n is 4 to 7, and a value of the command/addresssignal CA9 may be output to the DQS pad /DQS1.

At the time t₄, the clock enable signal CKE is activated with thepredetermined pulse width for one cycle of the clock signal CK, togetherwith activation of the logic low level of the chip selection signal /CS,and the command/address signals CAyR and CAyF, transmitted through thecommand/address bus 12, are input by the memory device 30.

The command/address signals CAyR are input at the rising edges of theclock signal CK at time t₄ and the command/address signals CAyF areinput at the falling edges of the clock signal CK (at the immediatelysubsequent clock edge of clock CK after time t₄). The command/addresssignal CAyR and the command/address signal CAyF input through thecommand/address bus 12 may be different signals (e.g., different sets ofbits of the test pattern).

In the calibration mode, the clock enable signal CKE acts as a readcommand of the command/address signals CAyR and CAyF, and thus when theclock enable signal CKE is activated at a logic low level, the values ofthe command/address signals CAyR and CAyF received by the memory device30 are output to the even DQ pads and the odd DQ pads are input by thememory device 30 at a timing responsive to clock CK.

After a delay of the predetermined time tADR from time t₄ of the clocksignal CK, the values of the command/address signals CAyR and CAyF (asinput by the memory device starting at time t₄) are output to the DQpads. That is, the command/address signals CAyR as input by the memorydevice 30 are output to even DQ pads and the command/address signalsCAyF as input by the memory device 30 are output to odd DQ pads.

When the memory device 30 transmits the command/address signals CAyR andCAyF to the memory controller 20, mapping with the DQ pads may be setvariously. As an example of mapping, values of the command/addresssignals CAyR input at the rising edges of the clock signal CK may beoutput to even DQ pads DQ[2n], where n is 0 to 9, and values of thecommand/address signals CAyF input at the falling edges of the clocksignal CK may be output to odd DQ pads DQ[2n+1], where n is 0 to 9.

As another example of mapping, values of the command/address signalsCA[3:0] among the command/address signals CAyR input at the rising edgesof the clock signal CK may be output to even DQ pads DQ[2n], where n is0 to 3, a value of a command/address signal CA4 may be output to the DQSpad DQS0, values of command/address signals CA[8:5] may be output toeven DQ pads DQ[2n], where n is 4 to 7, and a value of thecommand/address signal CA9 may be output to the DQS pad DQS1. Values ofthe command/address signals CA[3:0] among the command/address signalsCAyF input at the falling edges of the clock signal CK may be output toodd DQ pads DQ[2n+1], where n is 0 to 3, a value of the command/addresssignal CA4 may be output to the DQS pad /DQS0, values of thecommand/address signals CA[8:5] may be output to odd DQ pads DQ[2n+1],where n is 4 to 7, and a value of the command/address signal CA9 may beoutput to the DQS pad /DQS1.

At time t₅, the MRW#42 command, which is an exit command/addresscalibration mode command, is transmitted through the command/address bus12 together with activation of the logic low level of the chip selectionsignal /CS. In this example, the MRW#42 command is input at both therising and falling edges of the clock signal CK corresponding to thetiming t₅. That is, the same MRW#42 command is input at the rising andfalling edges of the clock signal CK corresponding to the time t₅.

There are many ways for the memory device 30 to recognize the signals onthe command/address bus 12 as a command (rather than another set of testpattern calibration information for a new cycle). For instance, theremay be a predetermined number of cycles of test pattern information sentto the memory device after which the memory device 30 expects to receivea command; the memory device 30 may count the number of cycles of testpattern information and when the count reaches the predetermined number(or one before or one after, e.g.) expect to receive a command.Alternatively, the memory device 30 may monitor all information inputvia the command/address bus 12 (monitor command/address calibrationinformation CA_(r) e.g.) to detect a predetermined code (e.g., a commandcode) and when the predetermined code is detected (and/or recognized asthe exit command/address calibration command code) exit the calibrationmode, or otherwise treat the input information as calibrationinformation resulting from the test pattern transmission during a cycleof the calibration mode.

After a delay of the predetermined time tMRZ from time t₅ at which theMRW#42 command is input, the output of the calibrated command/addresssignals CAyR to the DQ pads is terminated. A period from the time t₀ (atwhich the MRW#41 command, which is the enter command/address calibrationmode command, is input, to time t₅, at which the MRW#42 command, whichis the exit command/address calibration mode command, is input plus timetMRZ may correspond to a CA calibration mode period.

Although FIG. 10 shows only two sets of test patterns sent during thecalibration mode period (pair CAxR and CAxF and pair CAyR and CAyF),more than two sets of test patterns may be sent during a calibrationperiod. In addition, FIG. 10 illustrates the logic windows of thecommand/address calibration signals positioned to have its logic windowcenter correspond to the corresponding clock edges of clock CK. However,this is for description purposes only; it is contemplated that thecontroller 20 will alter the relative phase for each of thecommand/address calibration signals (representing the calibration testpatterns) so that the timing of the clock edge CK for many of thecommand/address calibration signals will be shifted in time (and may beof a timing which is shifted—such as outside of—with respect to thecenter of the command/address calibration signal logic window so thatthe memory device 30 incorrectly interprets the command/addresscalibration signal logic).

FIG. 11 is a table showing an example for describing mapping betweencommand/address signals and DQ pads according to another embodiment.

Referring to FIG. 11, values of the command/address signals CA[9:0]input at the rising edges of the clock signal CK may be mapped to beoutput to even DQ pads DQ[2n], where n is 0 to 9. Values of thecommand/address signals CA[9:0] input at the falling edges of the clocksignal CK may be mapped to be output odd DQ pads DQ[2n+1], where n is 0to 9. For example, in FIG. 10, values of the command/address signalsCAxR input at the rising edges of the clock signal CK corresponding tothe timing t₁ may be output to even DQ pads DQ[2n], where n is 0 to 9,and values of the command/address signals CAxF input at the fallingedges of the clock signal CK may be output to odd DQ pads DQ[2n+1],where n is 0 to 9. Values of the command/address signals CAxR input atthe rising edges of the clock signal CK at time t₄ may be output to evenDQ pads DQ[2n], where n is 0 to 9, and values of the command/addresssignals CAxF input at the falling edges of the clock signal CK may beoutput to odd DQ pads DQ[2n+1], where n is 0 to 9.

FIG. 12 is a table showing another example for describing mappingbetween command/address signals and DQ pads of memory device 30according to another embodiment Referring to FIG. 12, values of thecommand/address signals CA[9:0] input to the memory device 30 at therising edges of the clock signal CK (e.g., CAxR) may be mapped to beoutput to the DQS pad DQS0 and the DQ pads DQ[8:0]. That is, the valueof the command/address signal CA9 may be output to the DQS pad DQS0, andthe values of the command/address signals CA[8:0] are output to the DQpads DQ[8:0].

Values of the command/address signals CA[9:0] input to the memory device30 at the falling edges of the clock signal CK (e.g., CAxF) may bemapped to be output to the DQS pad DQS1 and the DQ pads DQ[17:9]. Thatis, the value of the command/address signal CA9 may be output to the DQSpad DQS1 and the values of the command/address signals CA[8:0] may beoutput to the DQ pads DQ[17:9].

FIG. 13 is a timing diagram describing a command/address calibrationmethod in the memory device 30 according to another embodiment. The bitorganization of the data DQ of the memory device 30 is 16X. In thecurrent embodiment, the command/address signals CA[9:0] are input atboth the rising and falling edges of the clock signal CK, and thus, eachcommand/address test pattern CA[9:0] may be composed of 20 bits. In thisregard, since the bit organization of the data DQ of the memory device30 is x16, the number of DQ pads is 16. The number of command/addresstest pattern bits sent with respect to a particular relative phasegenerated by the memory controller 20 is greater than the number of DQpads, such that the DQ pads cannot uniquely correspond to thecommand/address signals. As a result, the DQ pads may be allocated tothe command/address signals received on different signal lines of thecommand/address bus 12 at predetermined time intervals.

Referring to FIG. 13, in conjunction with FIG. 5, the memory controller20 generates the clock signal CK for the memory device 30. The memorycontroller 20 sends an enter command/address calibration mode command(or instruction) to the memory device 30 through the command/address bus12. The enter command/address calibration mode command may use theparticular MRS command format described elsewhere herein. The memorycontroller 20 transmits the exit command/address calibration modecommand through the command/address bus 12. The exit command/addresscalibration mode command may use the particular MRS command formatdescribed elsewhere herein.

At time t₀, the enter command/address calibration mode command istransmitted through the command/address bus 12, together with activationof a logic low level of the chip selection signal /CS. For example, athird mode register (MRW#43) command is transmitted as thecommand/address calibration start signal. When command/address signalsCA[9:0] of 10 bits are carried on the command/address bus 12, the MRW#43command may be a mode register setting command comprisingcommand/address signals CA[3:0] indicating the command is a moderegister setting command and command/address signals CA[9:4] indictingthe mode register setting command is an enter calibration mode command.

The MRW#43 command is input at both the rising and falling edges of theclock signal CK starting at time t₀. That is, the same MRW#43 command isinput at the rising edge of the clock signal CK at time t₀ and again atthe immediately subsequent falling edge of clock signal CK. This isbecause an error may be generated such that a memory device having ahigh operation frequency (e.g., during a DDR operation) misses ormisinterprets the MRS command. To reduce the chance of this error, thesame MRW#43 command is input at the rising and falling edges of theclock signal CK corresponding to the timing t₀.

At time t₁ after a delay of the predetermined time tMRW from time t₀ ofthe clock signal CK at which the MRW#43 command is input, the clockenable signal CKE is activated with a predetermined pulse width for onecycle of the clock signal CK, together with activation of the logic lowlevel of the chip selection signal /CS, and command/address signals CAxRand CAxF are transmitted through the command/address bus 12. The timetMRW may be a mode register set write cycle time.

The command/address signals CAxR are input at the rising edge of theclock signal CK at time t₁, and the command/address signals CAxF areinput at the falling edge of the clock signal CK at the immediatelysubsequent falling edge of clock signal CK after t₁. The command/addresssignal CAxR and the command/address signal CAxF input through thecommand/address bus 12 may be different signals. For example, when thecommand/address bus 12 is composed of command/address signals CA[9:0] of10 bits, the command/address signal CAxR of 10 bits and thecommand/address signal CAxF of 10 bits may be distinguished as differentsignals. Thus, the command/address signals CA[9:0] of 20 bits may beinput to the memory device 30 through command/address terminals (such aspads, pins or bumps—not shown) of the memory device 30 connected withthe command/address bus 12 of 10 bits.

As there is a demand for the memory device 30 to have a large capacity,the degree of integration and the number of memory cells increase. Asthe number of memory cells increases, the number of address bits foraddressing the memory cells also increases. The increase in the numberof address pins leads to the increase in chip size. Therefore, a methodfor suppressing the increase in the number of address pins required mostin the memory chip is desired. Since command/address signals are inputat both rising and falling edges of a clock signal in the currentembodiment, the number of command/address pins of the memory device 30may be reduced.

During command/address calibration mode, the clock enable signal CKEacts as a read command of the command/address signals CAxR and CAxF.When the clock enable signal CKE is activated at a logic low level, thecommand/address signals CAxR and CAxF are input at a timing responsiveto the clock CK, and results thereof are output as a data signal DQ.Thus, the clock enable signal CKE is used as a pseudo command.

After a delay of the predetermined time tADR from time t₁, thecommand/address signals CAxR and CAxF as input by the memory device 30are output as a data signal DQ. The time tADR may be a set delay timefrom activation of the clock enable signal CKE to data output to DQpads.

At time t₃, the calibrated command/address signal CAxR as input by thememory device 30 is output via the DQ pads of the memory device 30. Attime t₄, after the calibrated command/address signal CAxR is output tothe DQ pad for a predetermined time tADD, the calibrated command/addresssignal CAxF as input by the memory device 30 is output via the DQ padsof the memory device 30.

Mapping between the calibrated command/address signals CAxR and CAxF andDQ pads may be set in various ways. As an example of mapping, values ofthe command/address signals CAxR input at rising edges of the clocksignal CK may be output to the DQ pads DQ[9:0] and then values of thecommand/address signals CAxF input at falling edges of the clock signalCK may be output to the DQ pads DQ[9:0].

As another example of mapping, values of command/address signals CA[4:0]among the command/address signals CAxR input at the rising edges of theclock signal CK are output to DQ pads DQ[4:0] and then results ofcalibration on command/address signals CA[9:5] are also output to the DQpads DQ[4:0]. Values of the command/address signals CA[4:0] among thecommand/address signals CAxF input at the falling edges of the clocksignal CK are output to DQ pads DQ[9:5] and then results of calibrationon the command/address signals CA[9:5] are also output to the DQ padsDQ[9:5].

As still another example of mapping, values of command/address signalsCA[3:0] among the command/address signals CAxR input at the rising edgesof the clock signal CK are output to DQ pads DQ[3:0], a value of acommand/address signal CA4 is output to a DQS pad DQS0, values ofcommand/address signals CA[8:5] are output to the DQ pads DQ[4:0], and avalue of a command/address signal CA9 is output to a DQS pad DQS1.Values of the command/address signals CA[3:0] among the command/addresssignals CAxF input at the falling edges of the clock signal CK areoutput to DQ pads DQ[7:4], a value of the command/address signal CA4 isoutput to a DQS pad /DQS0, values of the command/address signals CA[8:5]are output to the DQ pads DQ[7:4], and a value of the command/addresssignal CA9 is output to a DQS pad /DQS1.

Starting at time t₄, the clock enable signal CKE is activated with thepredetermined pulse width for one cycle of the clock signal CK, togetherwith activation of the logic low level of the chip selection signal /CS,and the command/address signals CAyR and CAyF are transmitted throughthe command/address bus 12 from the memory controller 20 to the memorydevice 30.

The command/address signals CAyR are input at the rising edge of theclock signal CK at time t₄ and the command/address signals CAyF areinput at the immediately subsequent falling edge of the clock signal CK.The command/address signal CAyR and the command/address signal CAyFinput through the command/address bus 12 may be different signals.

After a delay of the predetermined time tADR from time t₄ thecommand/address signals CAyR and CAyF as input by the memory device 30are output via the DQ pads to the DQ bus 13. After the calibratedcommand/address signals CAyR (as input by the memory device 30) areoutput to the DQ pads, the calibrated command/address signals CAyF (asinput by the memory device 30) are output.

Mapping between the calibrated command/address signals CAyR and CAyF andthe DQ pads may be set various ways. As an example of mapping, values ofthe command/address signals CAyR input at the rising edges of the clocksignal CK may be output to the DQ pads DQ[9:0], and then values of thecommand/address signals CAyF input at the falling edges of the clocksignal CK may be output to the DQ pads DQ[9:0].

As another example of mapping, values of the command/address signalsCA[4:0] among the command/address signals CAxR input at the rising edgesof the clock signal CK are output to the DQ pads DQ[4:0] and thenresults of calibration on command/address signals CA[9:5] are alsooutput to the DQ pads DQ[4:0]. Values of the command/address signalsCA[4:0] among the command/address signals CAxF input at the fallingedges of the clock signal CK are output to DQ pads DQ[9:5] and thenresults of calibration on the command/address signals CA[9:5] are alsooutput to the DQ pads DQ[9:5].

As still another example of mapping, values of the command/addresssignals CA[3:0] among the command/address signals CAxR input at therising edges of the clock signal CK are output to the DQ pads DQ[3:0], avalue of the command/address signal CA4 is output to the DQS pad DQS0,values of the command/address signals CA[8:5] are output to the DQ padsDQ[4:0], and a value of the command/address signal CA9 is output to theDQS pad DQS1. Values of the command/address signals CA[3:0] among thecommand/address signals CAxF input at the falling edges of the clocksignal CK are output to the DQ pads DQ[7:4], a value of thecommand/address signal CA4 is output to the DQS pad /DQS0, values of thecommand/address signals CA[8:5] are output to the DQ pads DQ[7:4], and avalue of the command/address signal CA9 is output to the DQS pad /DQS1.

At time t₅, the exit calibration/address calibration mode command istransmitted through the command/address bus 12 together with activationof the logic low level of the chip selection signal /CS. For example, afourth mode register (MRW#44) command is transmitted as thecommand/address calibration end signal. When the command/address signalsCA[9:0] of 10 bits are carried on the command/address bus 12, the MRW#44command may be set by a mode register setting command which may compriseCA[3:0] to indicate the command is a mode register setting command andcommand/address signals CA[9:4] to indicate the mode register settingcommand is an exit command/address calibration mode command.

The MRW#44 command may be input at both the rising and falling edges ofthe clock signal CK corresponding to the timing t₅. That is, the sameMRW#44 command is input at both the rising and falling edges of theclock signal CK starting at time t₅. After a delay of the predeterminedtime tMRZ from the timing t₅ of the clock signal CK at which the MRW#44command is input, the output of the calibrated command/address signalsCAyR via the DQ pads is terminated. A period from the timing t₀ at whichthe MR_(W)#41 command is input to the timing t₅ CK at which the MRW#44command is input plus tMRZ may be a CA calibration period.

Although FIG. 13 shows only two sets of test patterns sent during thecalibration mode period (pair CAxR and CAxF and pair CAyR and CAyF),more than two sets of test patterns may be sent during a calibrationperiod. In addition, FIG. 13 illustrates the logic windows of thecommand/address calibration signals positioned to have its logic windowcenter correspond to the corresponding clock edges of clock CK. However,this is for description purposes only; it is contemplated that thecontroller 20 will alter the relative phase for each of thecommand/address calibration signals (representing the calibration testpatterns) so that the timing of the clock edge CK for many of thecommand/address calibration signals will be shifted in time (and may beof a timing which is shifted—such as outside of—with respect to thecenter of the command/address calibration signal logic window so thatthe memory device 30 incorrectly interprets the command/addresscalibration signal logic).

FIG. 14 is a table for describing a mode register command setting methodaccording to another embodiment.

Referring to FIG. 14, the MRW#43 command and the MRW#44 command may beset by the clock enable signal CKE, the chip selection signal /CS, andthe command/address signals CA[9:0]. The MRW#43 command may be set whenthe clock enable signal CKE is at a logic high level, the chip selectionsignal /CS is at a logic low level, the command/address signals CA[3:0]are at a logic low level, and the command/address signals CA[9:4] arerespectively at logic levels of H-L-H-L-H-H. That is, the MRW#43 commandmay be represented by a command/address signal CA[9:0] value of 2BH. TheMRW#43 command may be identical at both the rising and falling edges ofthe clock signal CK as noted above, however, a different value (such asthe inverse of 2BH) may be sent to the memory device 30 instead.

The MRW#44 command may be set when the clock enable signal CKE is at alogic high level, the chip selection signal /CS is at a logic low level,the command/address signals CA[3:0] are at a logic low level, and thecommand/address signals CA[9:4] are respectively at logic levels ofH-L-H-H-L-L. That is, the MRW#44 command may be set identically at boththe rising and falling edges of the clock signal CK. Herein, thecommand/address signals CA[9:4] may be used as mode register settingaddresses MA[5:0].

FIG. 15 is a diagram showing an example for describing mapping betweencommand/address signals and DQ pads of the memory device 30 according toanother embodiment.

Referring to FIG. 15, values of the command/address signals CA[9:0]input at the rising edges of the clock signal CK may be mapped to beoutput to the DQ pads of the memory device 30 DQ[9:0]. Thereafter,results of calibration on the command/address signals CA[9:0] input atthe falling edges of the clock signal CK may be mapped to be output tothe DQ pads DQ[9:0]. For example in FIG. 13, the values of thecommand/address signals CAxR input at the rising edges of the clocksignal CK corresponding to time t₁ may be mapped to be output to the DQpads DQ[9:0], and then the values of the command/address signals CAxFinput at the falling edges of the clock signal CK corresponding to timet₁ may be mapped to be output to the DQ pads DQ[9:0]. The values of thecommand/address signals CAyR input at the rising edges of the clocksignal CK corresponding to time t₄ may be mapped to be output to the DQpads DQ[9:0], and then the values of the command/address signals CAyFinput at the falling edges of the clock signal CK corresponding to timet₄ may be mapped to be output to the DQ pads DQ[9:0].

FIG. 16 is a diagram showing another example for describing mappingbetween command/address signals and DQ pads of the memory device 30according to another embodiment.

Referring to FIG. 16, portions of the values of the command/addresssignals CA[9:0] input at the rising edges of the clock signal CK may besequentially mapped to be output to the DQ pads DQ[4:0] at predeterminedtime intervals. Portions of the values of the command/address signalsCA[9:0] input at the falling edges of the clock signal CK may besequentially mapped to be output to the DQ pads DQ[5:9] at predeterminedtime intervals.

For example, in FIG. 13, after the values of the command/address signalsCA[9:0] of the command/address signals CAxR and CAxF are respectivelyinput at the rising edge and falling edge of the clock signal CK at timet₁, the values CA[4:0] of CAxR (as input) may be output respectively viathe DQ pads DQ[4:0] followed at a later time by an output of the valuesCA[9:5] of CAxR (as input) output respectively via DQ pads DQ[4:0].Then, the values of the command/address signals CA[4:0] of CAxF (asinput) are output via the DQ pads DQ[9:5], followed by the values of thecommand/address signals CA[9:5] of CAxF (as input) being output via theDQ pads DQ[9:5].

FIG. 17 is a diagram showing another example of mapping betweencommand/address signals and DQ pads according to another embodiment.

Referring to FIG. 17, portions of the input values of thecommand/address signals CA[9:0] input at the rising edges of the clocksignal CK may be sequentially output to the DQS pads DQS0 and DQS1 andthe DQ pads DQ[3:0]. For example, the values of the command/addresssignals CA[3:0] of CAxR are output via the DQ pads DQ[3:0], with thevalue of the command/address signal CA4 of CAxR output via the DQS padDQS0. Then, the values of the command/address signals CA[8:5] of CAxRare output via the DQ pads DQ[3:0], with the value of thecommand/address signal CA9 being output via the DQS pad DQS1.

Portions of the input values of the command/address signals CA[9:0]input at the falling edges of the clock signal CK may be sequentiallyoutput to the DQS pads /DQS0 and /DQS1 and the DQ pads DQ[7:4]. Forexample, after outputting the portions of CAxR as described above, thevalues of the command/address signals CA[3:0] of CAxF are output via theDQ pads DQ[7:4], the value of the command/address signal CA4 of CAxF isoutput via the DQS pad /DQS0, the values of the command/address signalsCA[8:5] of CAxF are output via the DQ pads DQ[7:4], and the value of thecommand/address signal CA9 of CAxF is output via the DQS pad /DQS1.

FIG. 18 is a diagram of an exemplary command/address calibration methodaccording to another embodiment. FIG. 18 is a timing diagram describinga command/address calibration method in the memory device 30 shown inFIG. 5, in which the bit organization of the data DQ of the memorydevice 30 is 16X. The method represented by FIG. 18 may be the same asthat described above with respect to FIG. 10 or its alternatives, exceptthat it may differ in the output of the command/address calibrationinformation from the memory device 30 to the memory controller 20. Inaddition, FIG. 18 illustrates an option of using the specific example ofMRW#43 as an enter command/address calibration mode command and thespecific example of MRW#44 as an exit command/address calibration modecommand. As the timing and operation of the memory system 10 of theembodiment of FIG. 10 and its alternatives has been described above, arepetitive description of the shared features of the embodiments of FIG.10 and FIG. 18 need not be repeated here. Mapping between the inputcommand/address signals CAxR and CAxF and the DQ pads may be setvariously. As an example of mapping, portions of values of thecommand/address signals CAxR input at the rising edges of the clocksignal CK may be sequentially output to even DQ pads DQ[2n] atpredetermined time intervals, and portions of values of thecommand/address signals CAxF input at the falling edges of the clocksignal CK may be sequentially output to odd DQ pads DQ[2n+1] atpredetermined time intervals, where n is 0 to 4. An example of this isdescribed further with respect to FIG. 19.

As another example of mapping, the values of the command/address signalsCA[3:0] of CAxR input at the rising edges of the clock signal CK arerespectively output to the even DQ pads DQ[2n], where n is 3 to 0, whilethe value of the command/address signal CA4 of CAxR is output to the DQSpad DQS0, while the values of the command/address signals CA[8:5] ofCAxR are respectively output to the even DQ pads DQ[2n], where n is 8 to5, and while the value of the command/address signal CA9 of CAxR isoutput to the DQS pad DQS1. At the same time, he values of thecommand/address signals CA[3:0] of CAxF are respectively output to theodd DQ pads DQ[2n+1], where n is 3 to 0, while the value of thecommand/address signal CA4 of CAxF is output to the DQS pad /DQS0, whilethe values of the command/address signals CA[8:5] of CAxF arerespectively output to the odd DQ pads DQ[2n+1], where n is 8 to 5, andwhile the value of the command/address signal CA9 is output to the DQSpad /DQS1. In this embodiment and all other embodiments describedherein, mapping and output of the other values of the command/addresssignals corresponding to later calibration cycles (e.g., other CAnR andCAnF, such as CAyR and CAyF) to the outputs of the memory device may bemade in a manner as described above with respect to CAxR and CAxF,although this is not necessary. In addition, while the mapping andoutput has been described above with respect to terminals (e.g., pads,pins, bumps, etc.) of the memory device 30, for all embodimentsdescribed herein, these descriptions are equally applicable toassociated buses and signal lines providing communications between thememory device 30 and memory controller 20, as well as to the terminals(pads, pins, bumps, etc.) of the memory controller. For example, adescription of an output of certain command address information (orvalues) to even DQ pads of the memory device 30 in a certain embodimentcontemplates the transmission of that command address information (orvalues) via corresponding even DQ lines of DQ bus 13 and receipt bycorresponding even DQ terminals by memory controller 20.

FIG. 19 is a diagram showing an example of mapping betweencommand/address signals and DQ pads according to an embodiment.

Referring to FIG. 19, portions of the values of the command/addresssignals CA[9:0] input at the rising edges of the clock signal CK may besequentially output to the even DQ pads DQ[2n], where n is 0 to 4.Portions of the values of the command/address signals CA[9:0] input atthe falling edges of the clock signal CK may be sequentially output tothe odd DQ pads DQ[2n+1], where n is 0 to 4. For example, in FIG. 10,the values of the command/address signals CA[0:4] of CAxR input at therising edges of the clock signal CK corresponding to the timing t₁ maybe output to the even DQ pads DQ[2n] while the values of thecommand/address signals CA[0:4] of CAxF input at the falling edges ofthe clock signal CK may be output to the odd DQ pads DQ[2n+1], where nis 0 to 4. At a subsequent time (which may immediately after thisoutput), the values of the command/address signals CA[5:9] of CAxR maybe output to the even DQ pads DQ[2n], and the values of thecommand/address signals CA[5:9] of CAxF may be output to the odd DQ padsDQ[2n+1], where n is 0 to 4. At a later time, calibration informationassociated with other calibration cycles may be output in a similarmanner, such as CAyF and CAyR described with respect to FIG. 10.

FIG. 20 is a diagram showing another example for describing mappingbetween command/address signals and DQ pads according to an embodiment.

Referring to FIG. 20, the values of the command/address signals CA[9:0]input at the rising edges of the clock signal CK (e.g., CAxR) may bemapped to be output to the DQS pads DQS0 and DQS1 and the even DQ padsDQ[2n], where n is 0 to 3. For example, the values of thecommand/address signals CA[0:3] of CAxR are output to the even DQ padsDQ[2n] while the value of the command/address signal CA4 of CAxR isoutput to the DQS pad DQS0 (where n is 0 to 3). Then, the values of thecommand/address signals CA[5:8] of CAxR are output to the even DQ padsDQ[2n] while the value of the command/address signal CA9 of CAxR isoutput to the DQS pad DQS1 (where n is 0 to 3).

The values of the command/address signals CA[9:0] input at the fallingedges of the clock signal CK (e.g., CAxF) may be mapped to be output tothe DQS pads /DQS0 and /DQS1 and the odd DQ pads DQ[2n+1], where n is 0to 3. For example, the values of the command/address signals CA[0:3] ofCAxF are output to the odd DQ pads DQ[2n+1] while the value of thecommand/address signal CA4 of CAxF is output to the DQS pad /DQS0. Then,the values of the command/address signals CA[5:8] of CAxF are output tothe odd DQ pads DQ[2n+1] while the value of the command/address signalCA9 of CAxF is output to the DQS pad /DQS1. The output of CA[4:0] ofCAxR and CA[4:0] of CAxF may occur at the same time. The output ofCA[5:9] of CAxR and CA[5:9] of CAxF may occur at the same time. At alater time, calibration information associated with other calibrationcycles may be output in a similar manner, such as CAyF and CAyRdescribed with respect to FIG. 10.

FIG. 21 is a block diagram showing another example of a memory systemthat may be used to implement one or more CA calibration embodimentsdescribed herein.

Referring to FIG. 21, the memory system 40 is different from the memorysystem 10 shown in FIG. 5 in that the command/address calibrationinformation CA_(r) (the phase adjusted calibration signal CA_(sp2) fromthe controller 50, as interpreted by memory device 60) is provided tomemory controller 50 through a separate calibration bus CA_Cal 15instead of the DQ bus 13. The calibration bus CA_Cal 15 may be dedicatedto transmitting received command/address information CA_(r) during thecalibration mode. When not in the calibration mode (during normaloperation), the calibration bus CA_Cal 15 may be used for anotherfunction, or may be unused. For example, calibration bus CA_Cal 15 maybe used to transmit DQ calibration information from the memory device 60to the memory controller 50 during a DQ bus calibration mode. The DQcalibration may be the same as that described herein with respect to anyof the CA calibration embodiments and the DQ calibration information maybe same as the CA calibration information, except that the calibrationis performed with calibration signals transmitted over the DQ bus, andthus a repetitive description need not be made here. Therefore, othersignals may be transmitted through a DQ signal line and a DQS signalline, which are additional lines, during calibration of command/addresssignals, thereby improving efficiency. To avoid a repetitivedescription, a detailed description of the same components as in FIG. 5will not be provided.

In the memory controller 50, the clock generator 201 generates a clocksignal CK to provide the clock signal CK to the memory device 60 throughthe clock signal line 11. The CA transmitter 203 adjusts the phase ortiming of the initial command/address signal CA_(sp1) in response to thecontrol signal CTRL of the phase/timing controller 208 to generate thephase adjusted command/address signal CA_(sp2).

In the memory device 60, the CA receiver 304 receives the phase adjustedcommand/address signal CA_(sp2) at a timing responsive to the internalclock signal ICK and as enabled by the clock enable signal CKE and chipselect signal /CS to generate the command/address calibrationinformation CA_(r). The command/address calibration information CA_(r)is provided by the memory device 60 to the memory controller 50 throughthe calibration bus CA_Cal 15. Through the calibration bus CA_Cal 15,the command/address calibration information CA_(r) is provided to thecomparator 206 of the memory controller 50.

The comparator 206 of the memory controller 50 compares sentcommand/address information CA_(s) (which may be data of the informationof the phase adjusted command/address signal CA_(sp2)—which may be thesame as the information of initial command/address signal CA_(sp1)) withthe received command/address calibration information CA_(r) to generatethe pass signal P or the fail signal F. The phase/timing controller 208generates the control signal CTRL instructing a phase shift of the phaseadjusted command/address signal CA_(sp2) according to the pass signal Por the fail signal F generated by the comparator 206. The CA transmitter203 generates the phase-adjusted command/address signal CA_(sp2)according to the control signal CTRL. During a calibration of thecommand/address communications between the memory device 60 and thememory controller 50, multiple cycles of sending phase adjustedcommand/address signals CA_(sp2), each with a different adjustedrelative phase with respect to clock CK, may be performed, and theoptimum relative phase between clock CK and command/address signals sentto memory device 60 from memory controller 50 may be chosen based onmultiple pass P and fail F determinations, as described herein withrespect to other embodiments (such as those describing memory controller20 and memory device 30 of FIG. 5). For example, by repetition of the CAcalibration cycle, the phase/timing controller 208 of the memorycontroller 50 determines an optimum relative phase of the clock CK withone, plural or all of the command/address signals to trigger input(e.g., latching) of by the memory device 60 at the middle of thecommand/address signal CA window. Thus, the memory device 60 receivesthe command/address signal CA for which the middle of an effectivewindow corresponds to rising and falling edges of the clock signal CK,which may be the rising and falling edges of both of the clock signalsCK and CKB.

Like other embodiments described herein, calibration may be performedfor a single command/address signal line CA (which calibration may beused to determine a single optimum relative phase for all signal linesof a command/address bus 12), for some but not all of thecommand/address signal lines of the command/address bus 12 or for all ofthe command/address signal lines of the command/address bus 12 (eitherindividually or as a group). The results may be used to determine andcontrol the relative phase between clock CK and the signal lines of thecommand/address bus 12 either as a single group (e.g., all of the signallines of the command address bus send signals having the same optimumrelative phase with clock CK), plural groups (i.e., each of the groupsof signal lines of the command/address bus 12 have a correspondingoptimum relative phase determined by the memory controller 50 and mayshare circuitry to achieve such determined optimum relative phase duringnormal operation—such as the CA phase/timing controller 208, orindividually (e.g., each of the signal lines of the command/address bus12 have a corresponding optimum relative phase determined by the memorycontroller 50 and may have dedicated (not shared) circuitry to achievesuch determined optimum relative phase during normal operation, such asa dedicated CA phase/timing controller 208).

FIG. 22 is a block diagram showing another example of a memory systemthat may be used to implement one or more command/address calibrationembodiments described herein.

Referring to FIG. 22, a memory system 70 may include a memory controller80 and a memory device 90. The memory controller 80 may include a clockgenerator 801, a command/address (CA) generator 802, a CA generationreference unit 803, a register unit 804, a comparator 806, aphase/timing controller 808, and data input/output units 810 and 812.The memory controller 80 provides the clock signal CK generated by theclock generator 801 to the memory device 90 through the clock signalline 11.

The memory system 70 additionally includes a CA reference signal lineCA_Ref 16. The CA reference signal line CA_Ref 16 transmits a signalCA_Ref_(s) and receives a CA reference calibration informationCA_Ref_(r) in the CA calibration mode of the command/address CAcommunications between the memory controller 80 and the memory device70. CA reference calibration information CA_Ref_(r) is provided to theCA_Ref Comparator 806 to determine a result (e.g., pass P or fail F) ofa cycle of the CA calibration, the result being provided to thephase/timing controller 808 to adjust the relative phase or timing ofthe command/address signal CA with respect to clock CK by providing acontrol signal CTRL to CA generator 802. Since a CA reference signalline CA_Ref 16 is provided, calibration of the command/address CAcommunications may be performed concurrently with transmission of thecommand/address signal(s) CA over the command/address bus 12.

The CA generator 802 generates a CA signal having a phase or timing thathas been determined (possibly adjusted) in response to the controlsignal CTRL, and transmits the same to the memory device 90 through thecommand/address bus 12. The CA generation reference unit 803 may beconfigured identically to the CA generator 802 (e.g., same circuitconstruction that may use the same unit cells from a cell library), andgenerates the sent command/address reference signal CA_Ref_(s). The sentcommand/address reference signal CA_Ref_(s) may be the same as orcompletely independent from the command/address signal CA generated bythe CA generator 802. The sent command/address reference signalCA_Ref_(s) may be generated with a phase determined by the controlsignal CTRL, which may provided by the CA phase timing controller 808(or derived from information provided by the CA phase timing controller808). The phase of the sent command/address reference signal CA_Ref_(s)controlled by control signal CTRL may be the same as the phase of a CAsignal(s) output by the CA generator 802.

The sent command/address reference signal CA_Ref_(s) is provided to theregister unit 804 to store the information represented by the sentcommand/address reference signal CA_Ref_(s). The sent command/addressreference signal CA_Ref_(s) is provided to the CA reference signal lineCA_ref 16 which transmits the sent command/address reference signalCA_Ref_(s) to the memory device 90.

The register unit 804 stores the information represented by the sentcommand/address reference signal CA_Ref_(s). The comparator 806 comparesthe information of the sent command/address reference signal CA_Ref_(s)stored in the register unit 804 with received command/address referencecalibration information CA_Ref_(r) received from the memory device 90via the data input unit 810 of the memory controller 80. The comparator804 compares information of the sent command/address reference signalCA_Ref_(s) stored in the CA_Ref Register 804 with receivedcommand/address reference calibration information CA_Ref_(r) to generatethe pass signal P or the fail signal F. In a manner that may be the sameas described herein with respect to other embodiments, the generation ofthe pass signal P or fail signal F is performed for each cycle of thecommand/address communication calibration (each cycle corresponding to atransmission of a CA_Ref_(s) at a particular phase), and the group ofpass P and fail F signals generated during the command/addresscommunication calibration mode may be used to determine an optimumrelative phase between command/address signal(s) transmitted over the CAbus 12 and the clock CK.

For example, the phase/timing controller 808 generates the controlsignal CTRL instructing a phase shift of the command/address signal CAaccording to the group of pass or fail signals P or F generated by thecomparator 808 during calibration mode. The control signal CTRL is usedto determine (e.g., adjust or maintain) the relative phase or timing ofthe command/address signal CA and the clock CK and generate thephase-adjusted command/address signal CA which is transmitted over thecommand/address bus 12.

The data input unit 810, which may be an input buffer and/or amplifier,receives the received command/address reference calibration informationCA_Ref_(r) from the memory device 90 through the CA reference signalline CA_ref 16 and delivers the received command/address referencecalibration information CA_Ref_(r) to the comparator 806. The dataoutput unit 812, which may be an output buffer and/or amplifier,receives the sent command/address reference signal CA_Ref_(s) generatedby the CA generation reference unit 803 and transmits the sentcommand/address reference signal CA_Ref_(s) to the CA reference signalline CA_ref 16.

The memory device 90 includes a clock buffer 902, a CA receiver 904, aCA reference receiver 906, and input/output units 908 and 910 (whichrespectively may be input and output buffers and/or amplifiers). Theclock buffer 902 receives the clock signal CK transmitted through theclock signal line 11 to generate the internal clock signal ICK. Theinternal clock signal ICK may have the same timing (e.g. phase and dutycycle) as the external clock signal CK, or they may be different (inphase and/or duty cycle, e.g.). The CA receiver 904 receives the chipselection signal /CS and the clock enable signal CKE, and thecommand/address signal(s) CA transmitted through the command/address bus12. The clock enable signal CKE may be used as a pseudo command whichacts as a read command of the command/address signal CA transmittedthrough the command/address bus 12 as described elsewhere herein. The CAreceiver 304 may receive the command/address signal(s) CA when the clockenable signal CKE is in an active state.

The input unit 908 receives the sent command/address reference signalCA_Ref_(s) transmitted from the memory controller 80 through the CAreference bus CA_ref 16, and transmits the same to the CA receptionreference receiver 906. The CA reception reference receiver 906 may beconfigured identically as the CA receiver 904. The CA receptionreference receiver 906 receives the chip selection signal /CS, the clockenable signal CKE, and the sent command/address reference signalCA_Ref_(s) transmitted through the CA reference bus CA_ref 16, andlatches the sent command/address reference signal CA_Ref_(s) at a risingedge and/or falling edge of the clock ICK (which may be the same time asor dependent upon the time of the edges of the external clock CK). Thelatched information of the sent command/address reference signalCA_Ref_(s) by the CA_Ref receiver 906 is the received command/addressreference calibration information CA_Ref_(r) which may or may not be thesame as the information represented by sent command/address referencesignal CA_Ref_(s)(for example, based upon the timing of the latchingresulting from the relative phase of the clock CK and the sentcommand/address reference signal CA_Ref_(s) during this cycle of thecommand/address calibration.

The received command/address reference calibration informationCA_Ref_(r) may be the same as information obtained from a signalreceived over the CA bus 12 which is output from the CA receiver 904 toa source internal to the memory device 70 (after inputting theinformation to the CA receiver 904 when the CA receiver 904 receives thechip selection signal /CS, the clock enable signal CKE, and thecommand/address signal CA transmitted through the command/address bus 12in response to the internal clock signal ICK). The receivedcommand/address reference calibration information CA_Ref_(r) istransmitted to the memory controller 80 via CA reference signal lineCA_ref 16 and the output unit 910.

The memory system 70 may perform plural cycles of the CA calibration, anexemplary single cycle being described as follows. The CA generator 802of the memory controller 80 adjusts the phase or timing of thecommand/address signal CA in response to the control signal CTRL of thephase/timing controller 808. The CA generation reference unit 803generates the sent command/address reference signal CA_Ref_(s), whichmay be the same as the command/address signal CA, and transmits the sentcommand/address reference signal CA_Ref_(s) to the memory device 90 viathe CA reference signal line CA_ref 16. The CA reference receiver 906 ofthe memory device 90 inputs the sent command/address reference signalCA_Ref_(s) at a time according to the internal clock signal ICK andenabled by the clock enable signal CKE, and generates the receivedcommand/address reference calibration information CA_Ref_(r). Thereceived command/address reference calibration information CA_Ref_(r) ofthe memory device 90 is transmitted to the memory controller 80 via theCA reference signal line CA_ref 16.

The received command/address reference calibration informationCA_Ref_(r) is provided to the comparator 806. The comparator 806compares the information of the information of the sent command/addressreference signal CA_Ref_(s) with received command/address referencecalibration information CA_Ref_(r) to generate the pass signal P or thefail signal F for this cycle of the command/address calibration. Throughrepetition of the foregoing CA calibration cycle, the phase/timingcontroller 808 of the memory controller 80 determines an optimumrelative phase between the CA signal transmitted over the CA bus 12 bythe CA generator 802 and the clock CK. This optimum relative phase maybe chosen as described elsewhere herein and may promote input (e.g.latching) of the command/address signals transmitted during normaloperation by the CA bus 12 by the CA receiver 904 at timingcorresponding to the middle portion of the command/address signal CAlogic window (e.g., such that the middle of the command/address signallogic window corresponds to an edge of the clock signal CK and/orinternal clock signal ICK).

While calibration of a single command/address signal CA of the CA bus 12has been described in the current embodiment, the calibration describedmay be used to adjust the phase of signals transmitted on all signallines of the command/address bus 12. This may be done using only thesingle CA_ref signal line 16 (applying its calibration results to allsignal lines of the command/address bus 12). Alternatively, the CA_refsignal line 16 may be one of plural CA_ref signal lines, each of whichare used to adjust a corresponding one or group of signal lines of theCA bus 12. In addition, each of the plural CA_ref signal lines 16 may bea signal line adjacent to the signal line(s) of the CA bus 12 that it isused o calibrate (e.g., immediately adjacent or within 2 or 3 signallines, e.g.). This may include plural CA_ref signal lines interposedbetween the signal lines of the CA bus 12. Also, in alternativeembodiments, the CA_ref line(s) 16 may serve other purposes during modes(e.g., normal operation) outside the CA calibration (e.g., transmissionof power or other information signals).

The memory controller and memory devices described herein may take manyforms. For example, the memory controller may comprise a semiconductorchip or may be a package (e.g., one or more chips encapsulated in aprotective casing, such as resin). The memory device may comprise asemiconductor chip or may be a package (e.g., one or more semiconductormemory chips encapsulated in a protective casing, such as resin). Thememory device may be a NAND flash memory (including 3D NAND flashmemory), DRAM, PRAM, RRAM and/or MRAM. The memory controller and memorydevice may be packaged in the same semiconductor package (e.g. a memorycontroller chip and one or more memory chips stacked together andencapsulated in a package). The controller/device package may be apackage-on-package (POP).

The controller may comprise a portion of a master memory chip which actsas a master for one or more slave memory chips, the describedcalibration being performed for command/address communications betweenthe master memory chip and one or more of the slave memory chips. Themaster memory chip and one or more slave chips may be stacked andcommunicate via through substrate vias (TSVs) such as through siliconvias of each chip connected to one another (where all or some of theclock line 11, the command/address bus 12, the DQ bus 13, the chipselect signal line /CS, the clock enable CKE, and the data strobe lineDQS described herein are formed by one or more of the through siliconvias). The memory controller and memory device(s) may be elements of amemory card (embedded or removable).

The memory controller and memory device(s) may be mounted on the sameprinted circuit board or plural circuit boards connected within a singlecomputing system, which may include printed circuit board(s) comprisingelements of a memory module, a motherboard of a computing device (forexample, a personal computer) or other printed circuit boards (such aswithin a mobile phone, personal data assistant (PDA), or computertablet).

For certain applications, controller and memory device may integrallyformed with the same monolithic semiconductor substrate (e.g., part ofthe same semiconductor chip). For example, the memory may be embeddedmemory in a microprocessor, a communications chip, or a digital signalprocessor.

Also, while the embodiments above have been described as relating to amemory system, the invention may also be used to calibrate othercommand/address communications outside of memory systems, such asbetween nodes of a motherboard interconnect for servers, computers, etc.to assist communications between devices attached to the motherboard.

Also, while the embodiments describe an example of the command/addresscalibration information transmitted from the memory device to the memorycontroller is the interpretation of the command/address calibrationsignal sent from the memory controller to the memory device (e.g., asinput by the memory device), however, other types of information may besent. For example, if the test pattern is predetermined (whetherprogrammed at manufacturing, or just prior the command/addresscalibration), the memory device itself may determine whether theinformation it has input is input without error to provide a pass P orfail F indication in response thereto to the memory controller.Alternatively, the memory device may contain logic to expect a certainrelationship between the a series of bits comprising the test patternsent during a cycle of the calibration, and/or between bits of the bitsreceived in parallel as part of the test pattern (and thus generate apass or fail signal to send to the memory controller).

Also, the calibration of the command/address communications has beendescribed to calibrate a timing for input of the command/address signalsinto the memory device, however, other types of calibration of thecommand/address communications may be performed. For example, for eachcycle of the command/address communication calibration, the controllermay alter a signal power, a terminal impedance (e.g., an adjustable ondie termination (pull-up and/or in series) of the controller and/or thememory device, and/or a duty cycle of the command/address calibrationsignal.

It should be noted that the description describes the calibration of acommand/address communications with calibration test pattern signalssent over a command/address bus. It is contemplated that certainimplementations will allow for certain, but not all, of the signal linesof a command/address bus to be shared for both command and addressinformation during normal operation. For example, a design may require22 address bits and 10 command bits which may result in one or more ofthe signal lines of the command/address bus that is not used to transmita command bit (e.g., if the command/address bus 12 consisted of elevensignal lines to transmit twenty-two (22) address bits (two sets ofeleven (11) bits in sequence), communications may require only ten (10)bits of a command on the eleven (11) signal lines leaving one of thesignal lines unused for command communications. As another example, allsignal lines of the command/address bus may be used for commandcommunications but some of the signal lines may be unused for addresscommunications (e.g., eleven bits for a command information and twenty(20) bits of address information may leave one of the signal lines of aneleven signal line command/address bus unused for addresscommunications).

While the inventive concept has been particularly shown and describedwith reference to exemplary embodiments thereof, they are provided forthe purposes of illustration, and it will be understood by those ofordinary skill in the art that various modifications and equivalentother embodiments can be made from the inventive concept. Accordingly,the scope of the inventive concept should be defined by the appendedclaims.

What is claimed is:
 1. A memory system comprising: a memory controller;and a memory device connected to the memory controller via a clocksignal line, a command/address bus and a bi-directional data bus,wherein the memory controller includes: a clock generator configured togenerate a clock signal, and to provide the clock signal to the memorydevice via the clock signal line; a command/address generator configuredto generate an initial command/address signal; a command/addresstransmitter configured to receive the initial command/address signal, togenerate a command/address signal based on the initial command/addresssignal, and to provide the command/address signal to the memory devicevia the command/address bus; a register configured to store informationof the command/address signal; a comparator configured to receive theinformation of the command/address signal, and to compare theinformation of the command/address signal with information of acommand/address calibration signal; a phase/timing controller configuredto generate a control signal, and to provide the control signal to thecommand/address transmitter; and an input/output circuit configured toreceive the information of the command/address calibration signal fromthe memory device via the bi-directional data bus.
 2. The memory systemof claim 1, wherein the memory device includes: a clock bufferconfigured to receive the clock signal; a command/address receiverconfigured to receive the command/address signal; and a datainput/output circuit configured to output the information of thecommand/address calibration signal to the memory controller through thebi-directional data bus.
 3. The memory system of claim 2, wherein thecommand/address transmitter provides first data and second data to thememory device via the command/address bus, and wherein thecommand/address receiver receives the first data at a rising edge of afirst cycle of the clock signal through the command/address bus, and thesecond data at a falling edge of the first cycle of the clock signalthrough the command/address bus.
 4. The memory system of claim 3,wherein the command/address receiver generates first calibrationinformation based on the first data, and to generate second calibrationinformation based on the second data.
 5. The memory system of claim 2,wherein the command/address receiver receives a chip selection signaland a clock enable signal provided by the memory controller via one ormore different signal lines from the command/address bus.
 6. The memorysystem of claim 1, wherein the command/address transmitter adjusts aphase or timing of the initial command/address signal in response to thecontrol signal, in order to generate the command/address signal.
 7. Thememory system of claim 1, wherein the comparator generates a pass orfail signal by comparing the information of the command/address signalwith the information of the command/address calibration signal.
 8. Thememory system of claim 1, wherein the memory controller includes acommand/address generation reference circuit configured to generate acommand/address reference signal that is transmitted to the memorydevice.
 9. A memory system comprising: a memory device; and a memorycontroller connected to the memory device via a clock signal line, acommand/address bus and a data bus, the memory controller including: aclock generator configured to generate a clock signal, and to providethe clock signal to the memory device via the clock signal line; acommand/address transmitter configured to generate a command/addresssignal, and to provide the command/address signal, first data and seconddata to the memory device via the command/address bus; and aninput/output circuit configured to receive first calibration informationand second calibration information from the memory device via the databus, wherein the memory device includes: a clock buffer configured toreceive the clock signal; a command/address receiver configured toreceive the command/address signal, to receive the first data at arising edge of a first cycle of the clock signal through thecommand/address bus, to receive the second data at a falling edge of thefirst cycle of the clock signal through the command/address bus, togenerate the first calibration information based on the first data, andto generate the second calibration information based on the second data;and a data input/output circuit configured to receive the firstcalibration information and the second calibration information, and tooutput the first calibration information and the second calibrationinformation to the memory controller through the data bus.
 10. Thememory system of claim 9, wherein the memory controller furtherincludes: a command/address generator configured to generate an initialcommand/address signal; a register configured to store information ofthe command/address signal; a comparator configured to compare theinformation of the command/address signal with information of acommand/address calibration signal; and a phase/timing controllerconfigured to generate a control signal, and to provide the controlsignal to the command/address transmitter.
 11. The memory system ofclaim 10, wherein the comparator generates a pass or fail signal bycomparing the information of the command/address signal with theinformation of the command/address calibration signal.
 12. The memorysystem of claim 11, wherein the phase/timing controller generates thecontrol signal based on the pass or fail signal.
 13. The memory systemof claim 9, wherein, in a normal operation mode, the input/outputcircuit receives read data transmitted from the memory device throughthe data bus or transmits write data to the memory device through thedata bus.
 14. The memory system of claim 9, wherein, in a calibrationmode, the input/output circuit receives the first calibrationinformation and the second calibration information from the memorydevice.
 15. The memory system of claim 9, wherein the data bus isbi-directional.
 16. A memory device comprising: a clock bufferconfigured to receive a clock signal through a clock signal line, and togenerate an internal clock signal; a command/address receiver configuredto receive a calibration command through a command/address bus, toreceive first data at a rising edge of a first cycle of the clock signalthrough the command/address bus, to receive second data at a fallingedge of the first cycle of the clock signal through the command/addressbus, to generate first calibration information based on the first datain response to the internal clock signal, and to generate secondcalibration information based on the second data in response to theinternal clock signal; and a data input/output circuit configured toreceive the first calibration information and the second calibrationinformation, and to output the first calibration information and thesecond calibration information through a data bus.
 17. The memory deviceof claim 16, wherein, in a normal operation mode, the data input/outputcircuit transmits read data through the data bus and/or receives writedata through the data bus.
 18. The memory device of claim 16, wherein,in a calibration mode, the data input/output circuit transmits the firstcalibration information and the second calibration information throughthe data bus.
 19. The memory device of claim 16, wherein thecommand/address receiver receives a chip selection signal and a clockenable signal.
 20. The memory device of claim 16, wherein the data busis bi-directional.